User blog comment:Fruitcakepuns/Strengthen Cats/@comment-24659969-20160607004121/@comment-24659969-20160608115738

You can not gain any + level from playing. Although clearing a sub chapter gives you cat food which can be used to play gacha or buy special cat you don't have. There also some cat units possible to obtain only once thru clearing certain stages in SoL such as the cylones, crazed stages or collab event stages.

Atm, you are still at SoL ch.6,  I recommend you to progress thru SoL until you obtain Ururun (ch. 18 Jailbreak Tunnel). If you are stuck, replay the stages before to bank exp for later while waiting for daily tickets or events which rewards catfood or gold tickets.

Watch for the weekly stages which drops powerups and tickets. You should always pay attention to those timed-chapter SoL as you should bank up your energy to play those stages. There also awakening chapters which grants true forms for special cats.