Or you could run an event where every day you log in and play at least 4 games you get an item. and the more days you play in a row the item gets beter every day for example.
day 1, Add Type C & D (7 days)
day 2, Pick up weople ( 7 days)
day 3, colour code + cross hair (7 days)
day 4, X2 + Double up (7 days)
day 5, 15k sp
day 6, 2 X 1pcs weopon bomb
day 7, perm weopen
Players who play the full 7 days in a row and plays at least 4 games will get gifts.