This isn't a guide but more of a friendly note really. I'd like to suggest to everyone reading this that they start playing arena until they reach six paths, if they already haven't due to a lot of reasons.
1. Konohamaru corps is a bad unit for power, but a great unit if you're one of those players that like to mess around against u're enemy or just play for fun.
2. The rewards in general from Genin to Six paths are worth the effort, lots of coins for group skills/strengthening (meaning more power),Many coupons (magatmas, if u want power) alongisde a few seal scrolls
3. If you think arena is hard right now, it'll become impossible to keep a steady win streak as a f2p, if u were to ever fight a P2W/P2P. Because right now the characters obtainable are limited, so all ppl use pretty much common characters alongside maybe garra/some pains. You also need to have a win streak to reach six paths, you get around 3-5 points for winning a match and around 20+ if you go on a streak. Tobi is currently the best F2P unit in the game until he gets nerfed and more and more ppl are getting Akatsuki members from shop each day.