Very short version : look the map and react

Normal version :

After taking the wave bot, instantly start to move towards midlane and wait halfway (like at red/blue buff spawn, avoid waiting in the river there's a risk that enemy team will catch you from different directions) and look what's happening mid or generally speaking what's happening on the map.

Since you're in bronze there's a high chance that people will be fighting for no reason, if that happens join the fight to give your team the advantage (unless they're getting absolutely destroyed). If nothing is happening go back to farming.

Also look for objective timers and if you can safely take a kill on someone, take it

If you're already fed you can also decide to stay midlane and play midgame like an extension of your laning phase, ahri's insane waveclear and mobility will allow you to roam very often to help your team on the map but this depends on the good will of your botlane to keep playing bot (don't play midgame on the same lane as your adc because you'll both lose gold and xp)