This build is OUTDATED. This means you will have to improvise to make it work. Builds are outdated when Power Pills (or Free Pills) are included in the strategy. Free Pills have been removed from the game because players stacked the pills with Power Pills Turbo.
Trap/Nuke: Trap Duration, Nuke Damage, Nuke Radius
Siege Mode: Turret Range, Turret Stun, Turret Damage
Catling:Cat Range, Cat Attack Speed, Cat Damage
Other: Heath (not free) , Regeneration, Health (free)
Health (Free) -> Siege Mode -> Turret Range -> Trap/Nuke -> Turret Stun -> Turret Damage -> Nuke Damage > Nuke Radius -> Trap Duration -> Cat Upgrades (any order)
Note: Buy Health/Regen whenever you feel like you need them.
First grab free health and siege. Play defensively and farm creeps until you can get range upgrade. Once you have the range upgrade you can slightly out range almost every turret in the game. When preparing to out range turret (the only one you can't being the second bottom turret on Ribbit) be away that you must siege at the perfect spot or you will miss or be within turret range. You should also note that Leon's tongue, Lonestar's bull, or even an enemy player pushing you slightly towards the turret could mean death.
After you have turret range buy trap/nuke. Place traps similar to Yuri mines. Cover commonly traveled areas such as jump pads, escape routes, and bushes. Traps can also be used specific to the enemy characters your playing. For example, if there is an enemy Froggy G, place a trap right before you siege. This way if Froggy G dashes you he will be trapped within turret range and most likely die. Also similar to Yuri mines, if you place a trap while the enemy player and yourself are touching they will become trapped almost autimatically. Be away that you do not want to place traps that an easily be jumped over or be wasted on creeps/Voltar drones. You can do this by placing them slightly above walking level, however, don't place them too high or the smaller characters will walk right under them.
Use the nuke as a crowed control/turret killing tool. It is slow and does not do great damage if not upgraded. However, most players will run when they see it coming. This means you can use it to help distract the enemy team while you push or make them back off from attacking your turret/creeps.
Next buy stun. Do not rely on stun as it is random. With stun you should be able to start hitting people with the nuke and punishing anyone that tries to 1v1 you. Next buy turret damage. This will make you chip away at turrets fairly quickly as well as deal substantial damage to anyone to gets within range. You should now have the dps to take down anyone at low health who enters your turret range. Try to siege up and block enemy escape routes during team fights. This may cause them to divide their attention between you and your teammates and get you many kills from low health fleeing enemies.
Now buy nuke damage/radius. You should begin to use the nuke as a burst tool now. Do not jump into siege near an enemy group without back up, even if you land the nuke on all 3 of them you will likely die in the process. Try to control choke points and use the nuke to bring down their turrets if you are able. Do not fire a nuke at an enemy turret if they are near and not in the direction of the turret. You don't want to die from a loss of your massive burst tool that you just used on a turret.
Buy Health/Regen whenever you feel like you need it. I suggest buying tier 1 healing early in the game as it helps you stay in the action longer. Something to remember is if you are 2/3 health or lower do not enter a fight unless you are sure you can win. As Derpl, you need to maintain high hp all the time if possible, because you cannot run effectively. If you get below 3/4 health and do not have Medican, get health from the jungle or shop. Do not keep fighting unless you have to.
If you do decide to run, try putting out a grid in front of the enemy whilst escaping, in hope that they will get caught in it, giving you a good chance to get away.