Nero Fest is hard to farm because I'm new, should I leave it alone?

Use the following formation,
This will take 7-9 Turns (Max)
Front: Your Highest level servant (Damage CE when obtained from roulette) - Georgios (lv1) -Support (Damage Bonus CE)
Back: Leonidas(Lv1) - Benkei(Lv25) - Mash
Mystic Code: Chaldea, yes the basic one.
Put the petal drop or any medal farming CE on your servants when obtained from the roullete or gacha/free gacha.

On your fist turn cast taunt on georgios and use evade on him, this makes he endures two turns, then your support its going to do the rest of the job, until your mlb the damage ce your high level servant with only aid you a little.

This is the formation i have been using in a new account that i maxing for a friend, i only have a heracles lv 50 in this account (this is the high level servant on this account) and with that formation i can clear any of the six quest without problem, for support i usually use a raikou, with all the used taunts i can survive to the last round with full hp and finish then off with just normal attacks (since all taunt servants are usually dead at this part of the quest and only have left the support or your high level servant you can chain attack and kill the servants in two turns or a NP in case i charge the bar during the battle), heracles now its lv 70 (thanks to the materials and drops from using this strategy), i obtainend all the damage ce from the roulette and mlb it (since i don't plan on passing the exhibition, i past the sumanai one, because i use my own emiya and he can solo sumanai), same for the petal drop now i have the four copy's.

You dont need apples for this since your low level the AP bar will refill each two battles.

It's in your best interest to farm Nero Fest event rather than anything else right now. Story can wait for this, and Ember farming won't provide anywhere near to the same amount of mats or even xp cards for your servants.
I'd strongly advise you to concentrate on this even rather than anything else.
Look for friends with strong support servants (that are equipped with White Rose CE) and use them to help you clear the farming nodes. See which highest farm nodes you can clear comfortably enough and do your best. Try to get all Joint Recital CE's asap as well.
Remember: As long as you try, at worst, you'll have a stronger lineup of servants after this event than you did before it (xp cards + mats + event CE's (Joint Recital one of best event CE's in game, which you might also MLB via farming).
Don't stress over Exhibition matches, and concentrate on farming Petals and rolling the lottery.