Anyone here plays S4 League?

At your level of playing you don't want to dedicate yourself to a specific weapon(s) just yet. Find weapons you like, then ask yourself what you like about it, and see if there's another weapon that can do it better. Then you start working towards mastery. The weapon I lead with is Revolver and I try to make myself use it as efficiently as possible (Pushback abuse, OHKO potential, etc). I'll go over some potent "easier" weapon combinations and some other stuff later.

For basics though you could watch this video guide that I made. It's focused on TD but the stuff I cover helps you with character control.

Some good Rookie level sets are:

PS, CS, or HG/automatic weapon/Revolver - HP+30 or Anchor if you're using PS or CS
melee or HG/automatic weapon/automatic weapon - HP+30
SMG/Semi/Smash - HP+30
HMG/automatic weapon/Sentry - HP+30, Shield or Wings
Bat/automatic weapon/automatic weapon - Invisibility

As for your preferences, unless your proficiency with a Railgun matches or surpasses your proficiency with other weapons, I would stay away from it. Otherwise:

Rail/Revolver/anything - Shield or Invisibility
Rail/HMG/automatic weapon - Wings or Shield

CautioN's railgun guide on Youtube is pretty useful for learning how to snipe, too. As for myself, I use Revolver/Smash/CS or HG with HP+30.

(Yes I would start posting on SP again just because there's a topic on S4, shut up guys)