What server specs should I get?

Assuming thats pretty much at your peak then probably yes, probably worth checking it a few times first though to make sure it doesn't go up all that much.

 

Try to sell to direct advertisers mate. You could probably sell banner ads, and in-post ads.

 

Ok, thank you for your help Bendo

Would you mean self managed openads based advertisements?

 

why aren't you using adsense?

 

No advertisements that are controlled by you - after being bought by advertisers.