i remember the days back on duckroad(cap 110,xp-sp-450x with pt 550x,item drop 350x and gold 50x)...every day like 1-1.5k ppl if not 2k(max of the server)...in other words:
-the cap:some players want 80-90-100-110 and other 110+...
-rates:not to low ,not to high; i think no1 wants to bot 24h/day to reach the max. lv in 2-3 weeks
-silks:u can make a vote 4 silk system and donate for keeping up ur server;also u can make contests like who buys the biggest amount of silks wins smth
-pve or pvp:i suggest pve since pvp starts to get borring after 1-2 weeks
-hire only trusted ppl who arent so corrupted...5-10 guys walking with special items aint such a big deal comparing with 50-100...
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-be prepared for problems and inconveniences like dos attacks/u dont have enough money to pay the root and etc.
-make a plan about how to run ur server properly in the following weeks/years..most of the servers run for about 1 week(1 month if they are lucky)and thn close down bcs they "don't have money" :P,i think this the most important thing for all the ppl who are trying to open a server...sry if i didnt use a proper english xDDD