Vainglory is a numbers game. The numbers you should be most interested in are gold and experience points. Gold and experience are award by killing (aka "last hitting") minions in both the lane and the jungle. The team with the most gold and/or experience points has a much higher probability of winning - i.e. the team with the bigger guns wins the fights.
In the lane and jungle there are a fixed amount of minions; however, the minions in the lane can only be killed by the appropriate team while the minions in the jungle are up for grabs by anyone. If a team was to take a larger share of the jungle minions, that gives them a gold and experience advantage while denying that gold and experience from the other team. This makes the jungle a valuable objective by itself.
If I'm playing in the lane and the enemy team is placing two opponents in the lane against me, here's how I view it:
Generally, there's a few things I do here to make sure I'm self-sufficient in a 2v1 lane:
Some other lesser known details: