Beat lane > Zone farm > Kill laner / Push lane > Roam mid > Get mid laner fed > Profit.
Beat lane > Zone Farm > Kill laner / Push lane > Invade enemy JG > Take camps / Kill enemy JG > Profit
Beat lane > Zone Farm > Kill laner / Push lane > Become 6/2 > TP Bot > GG
Also stop staying top to take 2nd tower. You should already be pressuring the map with your lead, even before the first tower. Unless your team still requires first tower, take that first asap if you think you can race enemy towards FB tower. Then start fucking roaming, if your enemy top is roaming as well ( but hes weak since you beat him ) take his 2nd tower, or counter roam if you think u can beat 3 v 3 / 2 v 2 / 2 v 3
Also how the fuck are you Bronze 4 for 3 seasons straight?
If you get a lead and you stay for second tower, your lead is useless for mid / bot. The only thing you're doing is denying an already underfed top laner from moving to pressure the map.
When your resources are better spent pressuring the map with your own lead, because if the enemy top laner tries to contest a 3 v 3 or 2 v 2 he is weaker therefore an even numbered fight is actually advantageous to you depending on the games situation.
There are a lot of factors you can tie into decision making, but obviously there's no general say in what you should do, it would take too long to list all the different scenarios and answers.
When you do decide to pressure / roam, make sure your execution on whatever decision you make is hasty and more or less guaranteed. This could mean a number of things.. factoring in enemy position / last seen, enemy vision, how overextended the lane you're ganking is, their summoner spells CD.
That way, you give a small window for top to farm up, because you'll be returning soon after sapping the enemies power elsewhere to keep the pressure going on their top laner.
The end result is total map domination, you'll take over the game with your lead, instead of keeping your lead isolated at Top Lane.
Obviously the higher elo you get, the harder this will be to pull off, solo carrying with a 2/0 lead.
You'll just have to gain more game knowledge and understand things a little better than the people at your current MMR.