>>5381506I would recommend getting figures you like the look of. My first custom was a Sea Quest action figure and he's too small and doesn't really match the rest of the scale of my other customs now. Make customs out of toys you like basically.
I use milliput. It's a two part epoxy putty that sticks to plastic easy and dries in about two hours so work in small amounts. But when it's wet it's like play-doh. Only 7$ and I've used it on 4 or 5 customs and I still have have left. Depends on how much you sculpt.
Paint wise, I started with a testors $12 starter kit from Amazon, it served me well but I kept feeling the paint was too goopy and thick, I recently bought citadel basics from Amazon for $50 after seeing multiple reviews and a YouTuber I follow use it.
Dremmel is nice and I just got one for Christmas but I think you could work around it until you're sure you want to stick with the hobby.
I'm working on a William "the fridge" perry now. I'm using a Wwe elite Mark Henry as the base. I already dremeled off his beard and dreads. Need to resculpt his hair and ears, then paint. Also some minor detail sculpting.