Decided to stay with 4ER for time being. Only 330000 tokens to max GBE (lvl 4 currently). I’ll max Boom Cannon (1 level to go) as well, as you get access to more further on Tech Tree. Will bank up to 500000 tokens before hitting 5ER. I have enough keys now to open ER, Shock, SL, Troop Health & Grens. I only attack when Chests are available and generally hit Legend Tier 1 to collect 100000 tokens.