Safelane Anti Mage

Play as selfish as you can, if you lose out on several waves/camps by having to TP (early/mid) game to have a 10% chance of saving your mid, don't do it. You'll only be griefing your own game.

You can definitely TP to towers when enemies overextend and are setting up for a mana void hit, especially pre battlefury as you'll be pushing slowly anyway; only do it if you have a < 10% chance of dying.. so after chronosphere, doom, global silence, etc, etc.

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If you have an annoying lane, you can trade your salve for taking away opponent's mana, in the long run this usually is better as you can just ship in more regen. If the lane sucks, just go jungle after a few levels, give your support solo XP. Mana break can help quite a lot to kill jungle creeps. If you know you won't be needing it, also don't be afraid using mana void to damage (stacked) camps after having drained a neutral with a decent mana pool.

And most important: don't engage in stand-offs where two teams are waiting for each other to make the first move; splitpush other waves/lanes, do jungle camps, just keep gaining gold and TP/blink once needed. If the enemy keeps you in a stand-off situation, it is basically the same as standing in the fountain.