How to progress into weighted chinups?

I currently weigh 90kg & still bulking so losing weight although an easy answer is not one that pertains to my goals. I can currently do 5x5 chinups; what would be the best way to increase my body weight chinups and when should I move on to weighted chins? The most common thing that I saw when looking around for answers is to do grease the groove with a pullup bar at home but no money to do this - What progression schemes have you found that work/can work?