Jump into MP and leech whatever you can get with a new char for the set conquest. Using ancients you surely have from your other char, you should be able to climb in difficulty fast and pretty soon you will be showered with sets. Maybe you have puzzle rings and stuff like that, good time to use it when you're up there.

You can just do barb so the crusader gear largely matches. The hardest part should actually be getting to 70. Make good use of the cube. Also barb is "nice" because you can just whirlwind mindlessly. Sets aren't too tricky either and generally just work for GR45, at least with some additional supporting item which you'll surely find along the way.