Ascension or something like it, permanently.

The main reason I say this is I feel we need a fun way to practice new champs.

Fer example I recently got Riven, practiced her in a bot match or 2, then took her into norms.

First two games I fed in lane, and had a REALLY shitty time in the next 30 minutes of the match.

In ascension you cant really fall behind. You can die a few times early, and still get even items, and still have fun.

Also I found it really fun mode in general, whoever I was playing.