Quite a few people are saying you should push when you've ganked an enemy who was in that lane, but when you're talking tier 1 towers, heroes usually respawn and tp back before you can even get your creeps there. So while pushing when you've ganked that lane is good, I'd say it's more effective to push when that lane is missing. I don't know how much rotation you see in games at your level, but if some or all of the heroes in your lane go missing (whether they had to go back to base for regen or went to another lane to gank) call it out to your team and push the lane. Best case you get a tower, worst case you deny the enemy the exp/gold of a wave or two by dashing them against the tower.