Level Kuro or farm Morgan/Buggy?

Hello, I'm kind of new to this game ^^(pirate Lvl 49)

I'm trying to build a slasher team.
so far i have
-Arlong (unevolved lvl 44)
-Zoro (36-Pound Cannon lvl 35)
-Tashigi (evolved lvl 34, lucky draw )
-Usopp (Golden Pound lvl 30)
-Kuro (unevolved lvl 25)

Since there is currently the Kuro event, i thought it would be a good opportunity to level my Kuro and evolve him, but then i saw that he needed 1.066.998 XP for lvl70!!! omg...  
wouldn't this take me a lot time and cost me tons of coins? :/

maybe i should rather invest more time in evloving Arlong and Zoro (both with max XP 392.109) and try to farm a Morgan (who needs "only" 261.406 max XP) instead of desperately trying to level Kuro to lvl 70 (1 million XP!). it seems like a big waste of time to me :/
i mean, Morgan will one day get his evolution and his stats arent so bad, right?

man, i wish i would have found this game much sooner, during the Buggy event... having Buggy would be nice
or maybe should i rather try to farm Buggy instead of Morgan?

any thoughts?

It is tough starting out, but IMO slasher team is the easiest to start. As far as the team members go you got enough. Don't farm for Morgan he is a joke compare to arlong. Two arlong is plenty of force DMG. Buggy would be a nice addition, but not a must. Zoro, tashigi / Kuro are the backbone of slasher team, and you got them all.

As far as leveling up your characters. You want to stick with the same color turtles for the 50% bonus. Best place to farm turtle is at the elite level on event island. Kuro is going on now which is perfect for you, since got two speed characters to level up. Focus on getting Tashigi to around 60, then start knocking out Kuro a bit. Next event is expected to be arlong which is weak vs speed, so farming continue. During next event you get red turtle time to evolve and lvl your arlong to 60 plus. You see the cycle now right.

alright, thank you ^_^
Kuro elite level is surprisingly easier than Alvida elite. Kuro expert level is too extrem, i died on the first stage lol
i'll never get that 1 free devilfruit, a bit sad...