1. Get a weapon pack, and tweak it in case of broken weapons (I've used one with an AWP with 10 shots). 2. Get good tools. SLAMs, Mine Turtles, play on a good server for examples. 3. PointShop for cosmetics, or if you will implement drops, weapons too. Some may not like it, but it's convenient 4. Scoreboard Ranks. 5. Custom HUDs (with HUD switcher). 6. A fancy loading screen. 7. RDM Manager 8. Mapvote
I'm actually starting a server myself, Although it will likely not last long due to my lack of interest over time.