Welcome! I also played competitive MTG for about a decade, and was highly involved in collecting, too. Late last year, I got back into collecting Pokemon, and ever since then I’ve lost most of my interest in collecting MTG. Pokemon is just wayyyyyyyyy more fun to collect.
I also happen to almost exclusively collect the EX Series – so I happen to think you’ve made a good choice on that front, as well. One piece of advice I’d give is to familiarize yourself with the pull rates. The pull rates of exs varied a TON between sets. There are some sets where each ex appears close to once per box, on average. And there are some sets where each ex appears closer to once ever 4 boxes, on average. That info is helpful when evaluating prices.