Start with stickers or decals over a clean regular polish manicure. Or maybe a good nail stamper if that’s what you’re drawn to. Actually painting with polish… it looks easy on social media because they have years of experience and a very practiced hand. But with a sticker, it looks finished right away, and you get practice with placement and figuring out what designs suit your nail shape.
If you do want freehand practice, put a little polish on foil and load a thin liner brush from that. Painting straight from the bottle brush is tough. Simple curves and diagonal lines are pretty forgiving, so you can do it while watching TV without having to redo your actual nails. You don’t need to run out and get the pro brands and hundreds of brushes right away. Keep it simple and keep practicing.
Hold off on gel at first. Uncured gel shouldn’t remain on the skin, and each layer needs curing with a compatible lamp for the time specified by the manufacturer. Regular polish is lower pressure for learning and much easier to remove when your first attempt looks better in your head than on your hand.