It is slow, but this is really the only way to level up.
I'm currently at level 54 with around 2 billion left and began using an autoclicker at min bet. Unlike other slot games this one does NOT reward high bets! Minimum bet of either 12k or 10.2k depending on the slot gives you 1 XP per spin while a 6m bet only gives you 26 XP. I figured I could start betting big at that point with between $1000-$3000 equivalent of in game currency and a goal of reaching level 120, but in a few hours I lost 10 billion.
I got really lucky and won a jackpot the first night to bring my chip count to 1.5 billion and then got lucky again the next night and won a 9.6 billion jackpot to bring my overall chip count to 12.5 billion.
