1) If you're finding the online playing a bit difficult, practice offline by creating a server and adding some bots of the difficulty of your choice. This way, you can get practice against them before adventuring out to the online world.
2) Stick with a bomb/hostage map for starters. My suggestion would either be cs_office, or de_dust (both eGO servers). They're smaller maps, and allow you to get the hang of the game in no time. Also, neither map allow AWPs, which are the noobiest weapon ever, so don't use them.
3) If you feel like a fun/interesting challenge, you should me in the eGO Jailbreak server. This server lets you have a practice at knifing, and surprisingly helps you with aiming the guns (as you need to aim quick in this server). If you don't know what Jail is, you can find the rulebook
here.
4) Other than those, a good server to play on would be a cs_crackhouse deathmatch server. Before I was in eGO, I played on those all the time. They're fast paced, fun, and give you eally good practice. You just have to not get annoyed by dying all the time. Unfortuanatly, eGO doesn't host a crackhouse dm server, but there are still some that are fun to play on.
That's just some tips about CS:S I can give you, regarding servers.
As for weapons, what everyone else said is true. You have to get used to the different types of recoil. Starting with an M4A1 (for CT) or AK47 (for T) are useful to start off with, but keep experiementing as you may find a new combo you like.
My weapon set I use, and suggest, is this:
CT:
Primary - M4A1
Secondary - Desert Eagle (or Deagle for short)
Other(s) - HE Grenade, Smoke Grenade, Flash Grenade (x2), Kevlar + Helmet
T:
Primary - AK47
Secondary - Deagle
Other(s) - HE Grenade, Smoke Grenade, Flash Grenade (x2), Kevlar + Helmet
That's all I got for ya mate. Hope it helped!
Feel free to add me on Steam if you see me in game. Forums too. I'm always willing to help!
~Vexx