You can have 4 camps Rook, it will just take you a while!! (lvl 20 stronghold required…)
I sit with 2 camps running lvl 13 elite training for the hopes of a 4*. Just because that’s what I need to advance now. If I had great 4* cards I’d probably put all my energy into feeder heroes to get my 4s up, instead of trying to get new ones. I only used this level of training once I had a team of 3s that I was happy with. (Because the 3*s churn out a twice the speed using training lvl 11!)
The other camp I’d switch between common, uncommon, extra low cost, and the lower elemental trainings as required/dependent on what materials I had.
… And right now I have a lvl 20 camp stuck doing research. Takes 7days and waaaay too much food!