Leveling

First, like you said you need a farmer. Since you didn't have any luck with summons so far I would stick with raoq 5, try to get around 1300 attack, rune him with fatal/blade and make sure you have at least all 4 runes in slot 2/4/6 and upgrade those up to +9 should be enough. If you need runes, just farm the scenario for it. I would suggest you to just keep raoq at 5* since you might pull a better farmer and farm faimon to make more 5. You will want to start working on the typical giant lineup bernard, shannon, darion, belladeon and orochi. You want to 5 those and get decent runes so you can farm b6-8. Then work on any good general monsters you might have like jojo, kona and potential good summons in future.

Energy usage

I would recommand you to use your energy to get your giant team to 5* first then start doing lower giant stages until you have decent 4* runes on all major monsters, then back to farming exp.

Teams/runes

Well for team, the average support team from giant does work in toa and arena. Rune wise, 4* can be fine until you get 6* monsters. I would recommand you to keep 500k mana at all time for ms in shop and great runes. Expanding shop slots is important too. For arena, I wouldn't bother too much about it until you have 5* team. Just use invites for glory points and reach as high as you can. For ad just put whatever synergize the most.

Misc

Personally, I would put on hold 9 tail until you get at least a full team of 5*. Fusing jojo isn't too bad since he will help you a lot in toa and since you don't have something awesome like lushen (lucky me was one of first summons). Save crystals for premium pack and in future for emergency buy. You want to get an eredas for sure if you haven't yet. For devilmons, keep buying them but save for better future summons.

Good luck summoner!

Edit: formatting