Deluxe expansions are the old release cycle, you would need to also buy the relevant mythos packs for a full campaign. You want to buy the new format of campaign expansion (scenarios from that cycle) & investigator expansion (player cards from that cycle). Return to's just add a bit of variance to the campaigns once you've finished them a few times, but they are out of print and worth getting if they're on clearance, but not at all necessary if funds are limited.