Do you have a controller or stick with a turbo option?
Take Ivy, go to custom character. Go to your Ai slots. On the first slot, where you change the ai behavior, turn down everything except rushdown and combo. Now for to her gear, and equip..look for modifiers like "does 15% extra damage to heroes" and shit like that. USUALLY strength effects strings, so for this you want to stack her strength (if unsure go to practice mode and look over her moves, it will list when something is effected by straight/ability) while trying to squeeze modifiers like % damage increase to heroes of villains or non-superpowered, etc. Go to the additional moves boxes. Look through your moves and read the descriptions, look for anything that mentions leading to follow ups or combos. These moves the ai uses to extend combos and really speed things up.
Once done, go to the second AI slot, and set it to zoning and runaway. Everything else to zero. Do the same with gear here except stack ability power and try to squeeze in modifiers like I mentioned above. There is a mod that does like 40-90% Inc block damage, this is good for the zoning ai if you have it on gear that's worth using. Now go to the extra abilities and look through them. There is a specific one that's SUPER helpful as Ivy, I forget the name but it's a.projectile.. of you don't have it, look.for any movement or runaway relevant specials or projectiles.
Now go to the Multiverse. Don't just do endless, you want to run ANY multi that gives you boxes, if you will.be around the PS4. Just run every multiverse that's there. Pick one, choose ai rushdown Ivy, start the Multiverse.
Once it's going, set your turbo controller to mash X. Then go do something else until she beats the entire tower. By mashing X it will advance to each new fight and even if it loses (highly unlikely) it will automatically restart and keep going. When she beats the tower, move to the next. Do this whenever you aren't playing the game.. it takes a few seconds to pick a new tower and you get good and keeping it busy.
Now, of you don't have time to micromanage, and need it to run longer term, you do Infinite. If you are around, do Infinite with rushdown ai, it's much faster. If you're going to bed or leaving or can't watch it for a very long time, you do zoning Ai, it kills slower but it almost CAN'T lose. Use the zoning AI for all boss Multiverses as well.
I've been doing this since release almost, though I haven't don't it steadily for very long, but I check the Multiverses all the time and always run the boss one that costs money, and keep an eye out on all the others for relevance, but if you're trying to stack gear,farming boxes is the best way. I have, with the exception of Raiden and Hellboy and I I think Manta, 40+ unique epics for every character in the game. If counting duplicates I'd have every single storage space maxed EASILY. I may have that many on Manta now too. With about 70% of the characters I have closer to 50-70 unique pieces.
If you're after gear this is the best way I know to get it. It's all random but this keeps your matches/credits/boxes per hour as high as reasonably possible a d since it's all random, volume is the name.of the game.. quantity.