Eep - you're not gonna like this answer. It's a waiting game. Gems and passes will be refilled after a period of time passes - about twenty minutes. And you will, unfortunately, max out on both, so you can't just leave the game for a few days and return. The only other way it, well, paying real money for currency. Go ahead if you think it's worth it, but the more patient among you will be able to play the game without paying.
How many passes do I need?
As we've mentioned, you'll need a pass for each new chapter, and there's five chapters per day. Right now in the game, there are 10 days - with more to be added in the future. That's a minimum of 50 passes required - for now. Yikes. So start stocking up if you want to see how this plays out.
Why do I need gems?
Gems are the second premium currency you'll need to collect, and this time it's so you can get personal with your chosen guy. Collect up gems and you'll be able to "graft" on a chosen partner, giving you plenty of quality time with them, and some cheeky extra scenes.
Why do I need passes?
You'll need passes in order to unlock each new chapter in Love Island: The Game as you progress. There's five chapters to each day on the island, so you need passes and quick. You'll soon run out if you're not careful, but that's exactly why you're here, isn't it?