Ok, so the first step is admitting you have a problem. You've figured out that your house is a relic from the dark ages and you need an update, so what do you tackle first and how? Even if you are on a budget, there are plenty of ways to come into the 21st century that won't break the bank.
My number one recommendation for updating is textiles. This includes draperies, pillows, shower curtains, bedcoverings, and rugs. New draperies and pillows in an updated pattern and color scheme will work wonders to instantly and dramatically change the look of a room. You can go all out and get custom ones made, or hit the internet and find some deals. Personally, I like to make my own because there is such an enormous number of indie patterns you can find at places like Spoonflower, but Target has some really nice things on offer too - no sewing involved. Floor to ceiling window treatments look best for a dramatic effect. Nobody "puddles" curtains on the floor anymore either, so make sure they clear the ground when you hang them. Throw pillows are great for sprinkling color around. Tie in with the colors in your new draperies and mix and match solids, or find a complimenting pattern in a similar color scheme. Plus, if your old pillows have gone flat, getting some new ones with a little bit of puff can help fix that tired deflated look. If you have the budget for it, also consider getting a new rug. I recommend getting a wool rug, they wear better and are easier to clean than a lot of synthetic rugs and will just look better overall for the long haul. Rugs can add a lot of color and texture to a room without breaking the bank. You can find plenty of good sized area rungs on places like Wayfair and Rugs.com for under $500. Colors can be a bit tricky if you buy online, so make sure you check their return policy before buying in case it doesn't look the way you envisioned. Bed linens are an easy thing to change as well. If you go with a bold pattern for your draperies, consider a solid or monochrome for a new bedcovering. New pillows, shams, and throws dress up a bed nicely too. And don't forget texture. Pillows are great for layering on beds, so pick some different types of fabrics like velvet, silk, or fur to give it depth. A shower curtain, in many cases, makes the bathroom and is a super quick change out with a lot of bang for your buck.
My second update recommendation is paint your walls. It is easy, it is cheap, it is not a marriage commitment - it's a wall color. I personally like bold colors, and no I'm not afraid of them because, guess what? it's not a tattoo. If it looks awful, you can always paint it again - ask my husband. A word of caution with bold colors though, unless you are reeeeely sure, stay away from yellow; it has a life of it's own and you don't want your guests to need sunglasses. I had a friend who painted a room bright yellow and it literally looked like an alien abduction was happening behind her bedroom door. Many paint retailers have tester size paints you can buy before you make the big commitment of multiple gallons. I highly recommend these. Grab a few of the colors you think you want and paint a 2' x 4' size area in your room to see how it will look in your space. Tip: It WILL look different in your home than it does in the store - I GUARANTEE IT. And it usually looks different in a larger patch than it does on the tiny color chip they give you. Some places, like Sherwin Williams, have larger letter size paint samples you can buy if you don't want the mess of test painting. If you want to save some money, consider doing it yourself, it's really not that hard. Yes, I know it is a pain in the rear to DIY it, but if you are tight on cash, it's a great way to save money and still get the look you want. Just make sure to do the proper prep and it will all work out beautifully! (More on how to do that in another post.)
Third, change your hardware. If you have shiny brass hardware, I hate to break it to you, but it is never coming back - not in this lifetime. Literally anything else would look better. Changing out a door handle is easy-peasy and will update the look of your house more than you would expect. If you buy in bulk, you can usually get a contractor discount at most big box stores. Tip: Count the number of doorknobs you have, make note of how many have or need locks and if any of them are dummies; it makes a difference. If you want the hinges to match (and you do) you don't necessarily need to replace them. Rather than replacing perfectly good hinges, which can cost surprisingly more than you would think, take them down and spray paint them and then re-install the same old hinges. Four bucks for a can of paint is way better than $400 for new hinges in the right color. You won't be touching these either, so the finish isn't going to rub off like it would if you painted a doorknob. Cabinet hardware is not terribly hard either. If you don't want to worry about drilling holes, just go with a new knob or handle depending on what you already have. Handles all come in standard widths so it's not hard to find a new one of the same size. If you can't decide, get several and take them home and test them in your space, then return the ones you don't want. I do recommend using a drill or electric screwdriver for this to save yourself from carpal tunnel.
Fourth, consider painting your furniture or cabinetry. Painting a piece of casework (especially if it is a golden oak monstrosity from the 80's) can give it a whole new life. You can go with something neutral, or pick a fun color - just like the walls, you can always paint it again if you don't like it or change your mind. I like spray paint for this purpose, but use what you feel comfortable with. Spray paint makes it easier to get in all those nooks and crannies, but it takes a little more patience. Just make sure you PRIME anything you paint. Go slow and do several thin coats, this is a multi-step process and trying to do it all in one go will not yield great results. Tip: to paint your cabinets, remove the doors and take them outside to spray. Brush or roll the boxes. Remove hardware or cover it with masking tape to protect.
Another fun way to update is to use wallpaper, which you can get practically everywhere now. There are lots of fun ways you can dress up a space or a piece of furniture with this stuff and if you get the peel and stick kind, it is low-commitment. You could inset some on a cabinet door face, place some on the back wall of a bookshelf, it looks really fun if you put it on the sides or your dresser drawers. A cool very designer-y thing to do is to put wallpaper on the risers of your stairs (that's the vertical face of the step.) It is unexpected and can look really high-end. Tip: If you are doing stairs, get a paper that you can apply sideways. Most peel and stick wallpaper is about 20" wide and stairs are generally 36" wide. If you put it on sideways, you can cover the riser with one piece of wallpaper instead of trying to match up the pattern along the width for every. single. step. Also, wallpaper is fun for an accent wall. But accent walls are "out," right? Yes and no. The solid color accent wall is out, a fun patterned wall can bring some serious drama to a space without overpowering it. Places like Rebel Walls have amazing large-scale mural patterns that are stunning for this purpose. Powder rooms are one of my favorites for an all-over wallcovering. They are small, so it's not a ton of money, and it creates a real sense of drama to be in a smallish space with all that yummy pattern. One of my go-to's for this is again, Spoonflower for the sheer number of options. Perusing their website is an event in itself. Lots of online retailers carry peel and stick too and you'll certainly find more online than you will in the store.
Light fixtures are another element that can make a huge difference in a home- similar to hardware. Designers call lighting the "jewelry" of a space. It literally gives the space sparkle. It also has the ability to make a space look really polished. If your old light fixtures are looking outdated or starting to pit or sag, think about getting some new ones. Make sure you try to coordinate them with the other metals in the space, like hardware so you don't look like your house got dressed in the dark. Using mixed metals in your lighting is a good way to tie in existing things you don't want to change but still want to match. If you don't know how to change out a light, you should be able to get an electrician to do it for you for $100 or under per fixture. If you have multiples you want to replace, ask for a discount - they will usually negotiate to get a bigger job.
Budget tip: For almost all of these recommendations, if you are going to have a professional install any of them for you, it is almost always cheaper if you provide the materials rather than leaving it to the contractor to buy them. Paint may be an exception if you need a lot of it because professional painters usually have discounts with specialty paint stores, but don't be afraid to ask upfront how much it costs. This can also reduce the amount of deposit you will need to pay, if any, to the contractor doing the work. Usually they will ask for an advance or deposit so they can purchase the materials for the job but if you are providing them, all they need to do is show up. This can reduce the risk of falling victim to an unscrupulous contractor, plus they still have a sense of urgency because they aren't getting paid until they show up to do the work.