I really enjoy making my own clothes because a) it's fun, b) you can do a bit of your own designing and get creative (which I love) and c) it's sometimes cheaper. I would not say that sewing is typically cost-effective. Fabric costs about as much as a typical bargain find in itself, a pattern AT BEST will cost you another $5 (and at worst $14-$17...what!?) and then you've still got thread, zippers, elastic, buttons, etc. In addition, chances are you are not an extremely accomplished seamstress. If you're not, what you make won't come out perfect...in fact, it might not even fit! (Usually it does, I'm just saying that you're taking a slight gamble, like buying something without trying on that you can't return.) If you sew and are on a tight budget, don't ever buy anything that isn't on sale. Patterns should be at least half off or below $5, fabric should be at least 30% off. Even with that, you're looking at spending upwards of $20-$30, not counting, of course, your valuable time.
One thing that I think is cost effective to sew would be fabric purses. They can often be made from fabric scraps or cheaply bought fabric, because they tend not to need as much fabric as clothing requires. They are so easy and you don't need a pattern. It's fairly self-explanatory. Cut out squares, leaving extra space for seam allowance, and piece them together. For the straps, cut long rectangles slightly bigger than twice as wide as you want the finished straps to be. Sew the long ends together, inside out, and then turn them right-side out and iron them. I should make a tutorial about this. But really, it's quite easy. If you want a lining, you can do that, it's just a bit more labor, and it isn't really necessary. One other thing that might be cost effective to make yourself would be flowy skirts without a pattern. You will still need about two yards of fabric, though, which can get costly. (For a skirt-making tutorial, see here.)
Ways To Save On Sewing
1. Always shop sales, and wait for the big ones.
2. Sew things that you can't buy - for example, sew with a fabric you adore, or make something you can't find or afford in stores. That way you're sewing smart, meaning you'll have to sew less, and the items you sew, you'll wear and appreciate more.
3. Scrap/fabric swap. To do this you need to find a sewing friend. Every time you make something, there is usually fabric left over. But matching-fabric purses are a thing of the past. You'll find yourself with excess fabric, which, even if you love, you don't want to have two things of the same pattern in your closet. So trade! You can trade online or with anyone you know who sews or wants to learn to sew.
4. Sew with a buddy. Patterns can be confusing, sewing can get dull, or you might just need a second opinion on something. It's a lot more fun with another person, it keeps you accountable to finish your project, and you can be a lot of help to each other! You can also take a look through your friend's patterns and see if you want to use one of them (if you are different sizes, you can add inches on around the outside of the pattern pieces, or fold the pattern in if you are smaller - don't cut down your friend's pattern).
5. Look outside the sewing store for cheap raw materials. Patterns can be found at garage sales or online, fabric can come from garage sales, or pre-existing clothes from the thrift store can be transformed easily and extremely cheaply.
6. Be aware of what you can sew without using a pattern. There are a lot of great online tutorials which are sufficient. I find videos to be especially helpful, since I'm a more visual learner. If you don't need a video, though, then clear, written instructions can be easier, since you don't have to start, stop, and jump around in the video. Things you typically don't need patterns for are purses, A-line skirts, aprons, shawls/wraps, capelets, blankets (of course) dog beds, leashes, collars, etc.
7. Find free patterns. Besides borrowing from a friend, sites like BurdaStyle have free patterns available! Of course, you have to print them off yourself. If you use your home printer, you have to piece together sheets of paper to make the pattern. If you take the file to a larger printer to get printed off for you, I hear it can be somewhat costly. Still, I think either is worth a shot! If you do purchase a pattern, get one that is basic, easy to change up, and won't go out of style. Simple dress and skirt patterns will prove themselves useful throughout your life. I recommend not cutting it down past the pattern's largest size - just fold in. You never know, you might want to make a different size for a friend, child, relative, etc.
8. Get creative with existing patterns. A dress pattern could be converted into either a skirt or top. Add or subtract elements to create an entirely different look. Ruffles, bows, pockets, etc, can all be added or taken away so that, when combined with a different fabric, it will make two projects from the same pattern look nothing alike! If your pattern has simple straps, you're in luck. Make them wider or more narrow, make it strapless, or convert it into a halter top (tie in the back or in a cute oversized bow over one collar bone). Add double straps and criss cross them in the back. The options are truly endless.
9. No need for sewing classes...check out youtube videos! Sewing machines and how to operate them can be mystifying, especially if you haven't sewn for awhile. Don't despair, just look up your sewing machine's make and model (it's written on the machine) with what you need to learn (i.e. how to fill the bobbin on a...).
10. Relax. Have fun! Every mistake can be undone (the seam ripper tool is my best friend) except for cutting. If you make it too big, just take it in a little at a time until it's right. If you make it too small, just give it away to a grateful recipient! If you mess up beyond repair, don't worry about it. It was a valuable learning experience, and you contributed to the success of a future project (don't give up). Chances are, you can still re-use the fabric for something else, even if it has to be a project which requires less fabric. Be forgiving of yourself and your finished project. If it looks homemade, chances are, you're the only one who can tell. No one really cares. And if you tell them that you made it yourself, they will be very impressed! So wear your finished product loud and proud.
Take your time, don't rush, and finish what you start. It is so gratifying to make something for yourself!