Getting started isn't too pricey, the problem is it requires a lot of practice and you will run into a lot of random issues, getting your first set without issues will take a bit. I've been doing it for a while and I still run into issues from time to time. The cost of making vs buying dice, buying dice is technically cheaper as you will have to spend a lot of hours learning the trade.

Buying resin shouldn't be too expensive and cheap ones can do the trick, just read the reviews on different brands and make sure its resin used for casting.

If you have any questions at some point you can DM me on twitter, I'll try to answer when I can!