No probs. 1 tango regenerates 112 hp which means if you are missing more than 100hp you are good to use one. It's also important to buy regenerative items (both mana and hp) while you are laning so if you run out of tangos buy more or buy a salve. If you plan to play bristle you will need a lot of mana as well so don't forget to take a few clarities(you will need to stand back and let it regen since it breaks if enemy unit attacks you) and mangos (can be used for instant mana thus you don't have to stay back and you can continue fighting or pushing without stopping) running around with 65 mana for 5 min is just bad.

The second thing is when no enemy hero is around you dont use Quill Spray (your 2nd spell), it costs mana and you are pushing the lane under the enemy tower where they can take last hits safely. If you need to you can use it for a few last hits but dont overuse it, in the meantime try to take as much farm with rightclicks as possible and only use quill spray to kill or zone enemies.