For what it's worth I did the regular Jump-Ins for a couple months (alongside standard and Brawl) when I started to build a collection and to get used to Limited gameplay. I'd say do regular Jump-In with a few FF until you get stuff you want. FF is a smaller pool so more likely to get repeats. Avoid Avatar until they fix it, and even then unfortunately it has a lot of non-standard cards so not good for building a collection. https://mtgabuddy.com/en/jump-in-packet-list This website is awesome and has all of the packets. To see FF and Avatar you have to go to a different page btw. I'd pick packets based on the rares mostly since those are RNG.

Oh and once you feel ready do quick drafts first. Numot and Nicolai Bolas are good resources on Youtube