I'm filling the dorms with T4 mates. What should I do next? I mean, which is the best tier to go after T4? And should I upgrade them to lvl 4? I'm doing a strenght build.
don't upgrade them. save all your pimdbank from hunts. put in 600m and/or 10b mates until you have 10k pimdbank saved; then sell all of it and put in a t7. at that point you should be high enough stats to continue with t7's until you're ~1.5mcs, when you should start putting in t8's and dont ug as soon as you can afford it; save some cash for DVP so you can sell stuff good luck!
I filled with 600m and then put 80b dorms in. You get mor bang for the buck with lvl 1 80b dorms than the 300b dorms so it's worth it to not skip 80b tier imo