Help with slasher team(?)

Hi,
I just started the game last week and got Arlong as first rare crew member so I made him my captain. He's in 4* mode
Rest of my crew is currently pound phoenix zoro, vista 4*, golden pound usopp and last spot I use hot rock stew sanji.
I would like to know which should I keep and which one should I try to get. I know sanji isn't really the best only used him for the heal.
Thank you

You currently have a fantastic team for a new player, best option currently for a balanced team would be to try and get kuro over sanji so you have a quick slasher (he is also currently the hardest hitting quick slasher). I would suggest you focus on leveling up and evolving the zoro first as he will be easier to handle cost-wise and actually has better atk stat growth than vista so putting exp into him is more beneficial. Next character to focus on is 100% vista as he is just an amazing character and can also be used to run tank int teams (same with zoro for dex) later on.

You could also try and get a morgan for a strong sub when up against dex bosses, fantastic stats for the amount of exp it takes to max him.

Thank you very much for the quick reply. I'll try to get Kuro since Morgan's event ending.
I dunno if good or not but I also have Izo.

If you follow panks reply you will get ashura zoro, who is a great dex captain. So Izo will be a good sub, if you will build up a dex crew in future so having her isn't bad at all. She can also used as a dex captain, but i would prefer ashura zoro. 
PS: She has a nice orb manipulation as special

Izo will be useful if you want to run a dex team against upcoming hina fortnight (which will also start the trend of fortnights giving the best exp/stamina by a large margin). As his special is fantastic on a dex team you might want to go with that for her island, don't know if you have any other dex chars so I can't say for sure. I would suggest using him in place of sanji when the island comes out though.

haha pank to people one thought. But yeah it is nice that we share the same opinion

Unfortunately I don't have any other dex members. Got rid of hacchi because I thought he didn't have any special ability, didn't see the evolved one had. Anyways guess for now I'll go with what panks said swapping sanji with kuro and keep the ret as it is. Maybe put in Izo depending on the situation.