There are tools like arma2 launcher that make the managing of mods extremely tidy and easy.
If you're stuck on what ones to get then you cant go wrong with ACE mod. Its pretty much a standard for all the milsim clans that existed prior to all the dayZ craze.
Each clan will 99% of the time have a map pack too. These almost always include, fallujah, duala, lingor, clafghan.
Most units also grab a weapon pack or two and a unit pack.
ArmA2 is a 5 year old game now (maybe more?) so the mod database is huge.
My clan has a very strict mod policy. But even so our modpack is large (90% of it due to maps).
We use ACE as a base, then we have a fairly large selection of islands we use. And a units pack. We dont do weapon packs because once you allow one in, the floodgates open and everyone wants this chopper, that jet, this ship, that gun this tank and it quickly ramps up over 10GB.
ArmA3 will be a fresh start. Our unit pack will be made custom for us so wont require replacement etc in future.
We're a very tight group of friends who play the game to a high level of skill and realism. That said our focus is always friends first players 2nd. We have a very skilled group of guys in server running, mission making, texturing etc. And would relish some fresh faces around out TS/Servers. We dont play all day every day but we generally play a mission or two that is custom made each weekend And often play a few evenings a week on insurgency or domination or something on weekday evenings.
We look mostly for guys who know what they're doing already and can work as a TEAM but if you show a willingness to learn and better yourself and contribute to a community we'll take on a new guy and teach them up.
If anyone is interested hit me up on our TS3 server:
ts3.st-alpha.net
anyone with the tags [ST-Alpha] can help you out. My name on there is JackSpyder.
http://st-alpha.net/activity.php here is our simple in progress website too.
We will be purchasing and testing arma3 but will remain with arma2 for campaigns and most gaming until arma3 reaches a stable enough state (mods too) to make the transition.
Edit: With arma3 being a steam service i guess ill give my steam profile:
http://steamcommunity.com/profiles/76561197996155180/ We dont use it as a communication tool but with the transition for arma3 it may be used more