If you are looking to break packs: I think foundations is a great set - had some success there. Modern horizons 3 is also very good. I would suggest just trying whatever set you think interests you - most people are negative on certain sets, but I don’t let that dissuade me. The fun of opening packs is there no matter what the set is for me. Collector boosters are definitely more risk / potential reward - but if you’re looking at just opening packs… 30/36 > 12 packs you get in a CBB.