If you don't want to kill the dragon lvl 3, don't need to buy potions (also you won't kill the birds without KNOWING HOW without any potions, so be sensate with yourself).

I'll explain by steps:
1 - kill the red buff. (if you have potions and wanna kill the dragon lvl 3, try to maintain your health and dont waste the potions)
2 - kill the birds ONLY IF YOU KNOW how, otherwise skip. (if you have potions and don't wanna kill the dragon, you can waste it with the birds.)
3 - kill the wolves
4 - kill the blue buff
5 - kill the toad.
6 - this step really depends if you feel lucky: You kill the river insect (i don't rememeber the name) to recover your life and go for the dragon. If you don't want to, or can't, just recall.
7 - buy 3 daggers or less, but waste everything with the 3 daggers (max 3).
8 - kill red buff if respawned (may respawn if you did some ganks meanwhile).
9 - kill the dragon.
10 - from now you are on your own, good luck!