A few classes to get you started are a good idea, if none of the other recommendation works you can also ask your local fabric store. (better if it is a local or small business, big chain stores might not know about that sort of things)
If the budget is really tight handsewing is always an option but it takes a lot more time. You could also attempt a bit of embroidery as a start, it's not quite like sewing but still involves a needle and you can get a cute result faster.
Depending on your location there might be day classes, but if you are somewhat remote then your best bet is buying a sewing machine, watching youtube and following along with some beginner patterns. Singer, brother, janome are decent brands with decently cheap entry level machines.
You can get cheaper second hand ones but that comes with a risk that the machine has a fault or needs something done to it that as a beginner might throw you off. Same deal with the very, very cheap machines some might work just fine, but theres a chance that it chews fabric or breaks threads and as a beginner it will be harder to tell if its the machine or you. So a cheapish branded one is a safer bet.
You could also start with hand sewing, its cheaper again. All you need is a needle and sone thread. But Id say its harder than using a machine and takes longer to finish projects. It would be fine if you wanted to start by mending small tears and fixing buttons. But really hand and machine sewing are two very different beasts.
To add to the notes about getting a sewing machine, they're something that can be found at a lot of makerspaces, and I've also lived in several cities where you could check one out from the local library.
If you want some project ideas to start with smaller projects would be a tote bag, little cinch purse, scrunchies. Cute hammock and cage accessories if you have a small animal pet. A gathered skirt with an elastic waistband is also a great starting point as it's more forgiving for measuring. Apron patterns would also be simpler and make good projects.
Cottons are generally less slippery than polyester and are easier to cut and sew since the layers will stick together better as you hold them instead of sliding against each other.
Stick with standard polyester thread to start.
I hope this helps with picking some projects and fabric. But don't be afraid to try something if you really love the project idea. The best way to learn is to try! Good luck
My first experience with sewing was with things like cross stitch and embroidery - it's really approachable and there are lots of nice little inexpensive kits out there that'll teach you the basics of hand sewing and have everything you need to do it.
Alternatively like people have suggested you could make something small like a pouch or bag - my first little project was a dice bag and I'm really satisfied with how that turned out!
You should give it a go! Do you want to learn hand sewing or using a sewing machine? And what kind of stuff do you want to make? I learned a lot from youtube tutorials and took a class for some techniques I couldn't figure out by myself.
Have you hand sewn before? You can actually do a lot of projects with hand sewing. It's obviously slower than machine sewing, but has a much cheaper start off point.
You're thinking machine sewing I assume? It's best if you can find someone with a sewing machine to take you through how the machine works and help you try some seams. If you don't have someone to help you, you can check for classes (for instance from a local quilt shop or community center), and acquire a machine to practice with. Some libraries have machines you can use, or get a cheap basic machine from someplace like Walmart. You might also get lucky finding a machine at a thrift shop but make sure it works before buying.
Have you already checked YouTube for tutorials? When I took home-ec back in high school we started with learning how to cut fabric and pin it together, how to properly thread the machine, how to operate it safely (there is a lot of force and moving parts and you have pins everywhere) and practiced sewing straight seams on two layers of cotton. Our first project was a draw string bag. If you want to start really basic you can always do some hand stitching (running stitch) to get a feel for how the fabric behaves and how to piece things, and plus that's a good skill for basting when you are machine sewing.