Just don't advance too much in the explorations. Just stay where you can "farm" the cards. If you get 3 Chance nodes, and if you have the selected card at lvl 100, you can get pero according to its rarity (300 for N, 700 for R, 1500 for SR). It's a very good way to make money.

if your stamina is lower than 200, explore using the event pool, not ghq nor quest (3 stamina against 10-20 from other modes).