These commands will allow you to quickly and efficiently buy your weapons at the start of a round.
(It may take some memorization or a cheat sheet)

-Here are the commands-

bind "KP_HOME" "buy ssg08"
bind "KP_UPARROW" "buy awp"
bind "KP_PGUP" "buy g3sg1; buy scar20"
bind "KP_LEFTARROW" "buy galilar; buy famas"
bind "KP_5" "buy m4a1;buy ak47"
bind "KP_RIGHTARROW" "buy aug; buy sg556"
bind "KP_END" "buy mac10;buy mp9"
bind "KP_DOWNARROW" "buy mp7"
bind "KP_PGDN" "buy p90"
bind "KP_INS" "buy p250"
bind "KP_DEL" "buy defuser"
bind "KP_SLASH" "buy smokegrenade"
bind "KP_MULTIPLY" "buy hegrenade"
bind "KP_MINUS" "buy flashbang"
bind "KP_PLUS" "buy incgrenade; buy molotov"
bind "KP_ENTER" "buy vesthelm; buy vest"
bind ins "buy nova"
bind home "buy xm1014"
bind pgup "buy mag7; buy sawedoff"
bind del "buy deagle"
bind end "buy elite"
bind pgdn "buy fn57; buy tec9"
bind leftarrow "buy bizon"
bind rightarrow "buy ump45"
bind uparrow "buy negev"
bind downarrow "buy m249"

There are two ways to apply these binds:

(1) Put these commands in an autoexec.cfg file, use notepad then save with extension .cfg then put [exec autoexec.cfg] at the end of your config.cfg file. The bind commands includes everything except for the "Taser" gun and "Decoy" grenade. Also note that if you are purchasing a Kevlar Vest/Helmet, it will purchase both if you have $1000, if not it will purchase the Kevlar Vest only. The configuration file is located in the following folder:
[C:\Program Files (x86)\Steam\SteamApps\common\Counter-Strike Global Offensive\csgo\cfg]

(2) Copy (CTRL + C) & Paste (CTRL V) the commands into CS:GO's console (open the console with ~).

FAQ:

Q: Why can't I open my console with "~" ?
A: Make sure you have console enabled in the settings, or check to see if you have the key set to something else.

Q: I can't locate my config file!!
A: Make sure you went to the location stated above. A common mistake is not going to the Program Files(x86).