Only 15 people have connected? or only 15 ppl max have been on at a time?
Get regulars, offer people to join your clan..Good pings help, good mapcycles count..Plugins that you run will help, but if you are planning to give people admin, I suggest not getting amx_super or UAIO..(ABUSE MAGNETS)..Put maps on your server like de_dust2 and de_rats(very popular on my server)..
Optimize your server:
http://support.steampowered.com/cgi-...i=&p_topview=1
If you are running your server thru steam, upgrade to HLDS.