hello

1. Code your own addons if you want a higher chance of being successful, don't just rip things off Gmodstore or leak things. Admins mods are a necessity.
2. Typically $20-$50 depending on how many slots, the kind of machine, and what host you use. Webhosting is often included for free. Addons on Gmodstore can get expensive pretty fast if you don't want to learn to code.
3. Start with whatever gamemode you want. Starting with one gamemode over another won't prepare you any better.