Tips on Mountain Lily... there's really none. Just get her with as much equipments/skill level as you can, level her up,evolve her, and use her until you have 20 units better than her, which will take a lot of time to happen if it ever happens.

And about teams, it has been answered a couple of times here and there and there is not a rule set on stone, but what most people do is:

In your fisrt set of 20, just order them automatically from power high to low, that'll make your strongerst squad 1. You make chance a unit manually if you see that your squad 1 is too slow (And if you think the machine got it wrong, as power soting is not 100% accurate, but that's nitpicking on my part). And then proceed to not use that set. This is done for the allies, since they will see your fist squad from the first set, so putting all your best in there helps your allies.

Then, for clearing maps and daily routine, you use set 2, where you want a much more balanced distribution, with most of the power divided between 2 to 4 squads. It's hard to say if it's better to have 2 strong 2 weak, 3 less strong 1 weak or 4 balanced teams. In the end, you want your teams tobe able to kill pest nodes and hopefully bosses, as they'll be taking different routes, so you can 3* the map.

If you are new, i would personally recommend splitting your power in 2 teams and then, once those 2 teams are competent to clear whatever path they go to (if they aren't already), make the 3rd team competent too.

Also, about levelling, if you are somewhat gold efficient, you should stop feeding lvl 5 manyus to lvl 30+ (or 40+) girls, so you'll eventually even up your teams as your girls get to lvl 30. And, of course, replace the 2* with 3*, the 3* with 4* and so on.