Pudge works in early and in mid game, if farmed well, can totally work even in late, but for have a good pudge, you've to have good team as well.

Explication time!: Start!

Boots: Needs for some speed in the early, you need it.
Tangoes: Fresh trees.

Early:

Tranquil : A good reg on pudge is a must, plus, it gives you armor and speed.

bottle : Hook costs mana , and of course the enemy doesn't ignore you.. so Life costs too, you need both

smoke : Wards are your enemies

Mid :

Blink OR Force staff : you need it, but it requires skill
Aghanims : Decreased cd , more damage for the hook

Late :

Radiance : stacks with rot and gives more damage.
Tarrasque : makes you tanky and gives you strenght you can stack in your ulti
Ethereal : Takes away magic armor from the enemy.. fresh meat!

your choice :

Power threads : Can work for the + 8 strenght and for the good auto.
Bloodstone : more kills you do, more you're unstoppable (change it with bottle)
Pipe : For go against nukers
Cremisi : For go against fisical damage
Blade mail : if the damage is too much and your enemy is pretty squishy (Sniper, drow ecc..)