I've heard good things about 2c-e and/or 2c-i and MDMA. Never tried it myself but I'd like to.
As for tolerance, I find visuals decline slowly with repeated use with a couple days or less in between. The headspace of the peak will be dampened unless you give it a good 5-7 days, although as long as you give it at least 3 days or so the tolerance won't be extremely dramatic. I've never cared to take 2Cs enough days in a row to get to a point where my usual dose wasn't still a strong several hour +3 experience, but repeated use makes the peak much less intense. Overall, I would recommend a waiting period that scales by intended dose. If you are taking low-ish dose for an enjoyable stimulating body high with slight trippy elements, you can get away with more frequent dosing and still attain the desired effects (how safe you decide frequent dosing of an RC, even a seemingly quite benign one like 2c-e, is up to you). If you are taking 20+mg to experience an intense trip, I recommend waiting at least 4 days and ideally 7+. By the two week mark at the latest, I'd say any tolerance/receptor downregulation should be pretty much gone, although some people find subjectively that longer waits make the trip seem more 'special'.
So: if you go on a 2C bender, don't expect the latter nights to be as intense, but it's doable and in my experience fairly enjoyable if you like the body high of 2Cs. As for tolerance, I believe the only tolerance effect going on is 5HT2a receptor downregulation - basically, your brain tuning down its sensitivity temporarily due to prolonged heavy stimulation - which most people seem to experience with virtually all serotonergic psychedelics.