I do a fair bit of sewing, when I get the time. I have a Brother sewing machine. But the main thing is, if you go somewhere like John Lewis, they'll try to sell you a fancy bells-and-whistles machine. Don't buy it. What you need is a machine with:
a nice easy action forwards & backwards
automatic buttonhole capacity
good zig-zag or other kind of raw seam finish
a good stretch stitch
easy to thread
Then get some simple patterns - Butterick, Simplicity, Vogue (although some Vogue patterns need advanced knowledge) - and follow the instructions. I find Vogue patterns are worth the extra expense as they have detailed instructions, and are cut really true to size.
There are some good sewing books on the market: I have found great ones in charity bookshops - the Good Housekeeping series is excellent.
Avoid the "Tilly and the Buttons" sort of stuff that's become fashionable. It's expensive, the patterns are not well-cut, and you won't learn proper sewing techniques. There's a similar sort of shop in my town & I went for a browse and was shocked at the fabric prices - ripping off people like you who want to get started but don't know how. £10 a metre for poly-cotton! £1 per button. No thank you very much.
If you have a local, independently run sewing machine shop, start there. It'll usually be run by a knowledgeable middle-aged to older woman, who knows her stuff. And you can talk through the kind of machine which will suit you for what you want to do. Also buy the best, sharpest, heaviest pair of scissor you can afford (and hold). And a good tape measure, and some long thin pins - don't get the bobble-headed ones, or the short thick (cheap) pins.
I go to a local market and buy cotton for a couple of pounds a metre and make up new patterns in a practice garment (a toile ) to get the fit right, and then use that to make adjustments to my paper pattern and then cut more expensive material.
You need a clear table or desk, and a good light & some patience. It's a great hobby & wearing your own-made clothes, fitted to fit you, not some manufacturer's weird view of the female body proportions, is great! And you'll never see someone else wearing your dress.