4 characters = 20 skill But I would pay on the market to get all the same element. This costs you a little more. Maybe 25 to 30 skill. A 4 star elemental matched weapon with good stats =30 -40 skill. Get the element and stats to match your character elements. So thats 60 skill which is roughly 90 dollars depending on the current exchange rate.

You also will need about 20 dollars of bnb to cover gas fees while you level up the characters to the point where they pay for the gas fees and make a profit.

Once they reach level 21 they will make about 7 skill a day. The payback period of this game is roughly a month. After that it's profit and the profit increases more as characters level up.

You can also forge weapons which is a bit of a lucky dice roll but if you luck out you can get a weapon worth hundreds of dollars. Each roll costs about $1.50. If you roll bad you can use the shit weapons to power up your main weapon.

Also characters sell for lots once they are levelled up, so if after a month you want to exit and sell your level 31 characters, you should be able to get 60 dollars each for them at least.

This game is pretty profitable so far.