Use the multiplier to jump to the high end of the range, then build up your Mortys.. There's no sense in reaching level 30 and taking your time to get to 39.. you are battling the same players, regardless. Might as well get to 39 as quickly as possible... then put on the brakes. That way you have access to the highest possible wild Mortys for capture and individual Morty XP.
You make a fair point though.
Well then get your shit together, get it all together and put it in a back pack, all your shit, so it's together. And if you gotta take it some where, take it somewhere, you know...