I am new and have a few questions

I am new to Airsoft and I need some help. First of all I have multicam pants and combat boots. I also have an M4. I am getting a multicam shirt but I don't know if I should get a black or multicam vest? 1.) What do I need all in all?
2.) how do I join a team?And what team should I join?
3.) should I get a red dot site or iron sites or a laser?
Please reply, as I said I am new and need some help.