Need tips on Doom

Order of preference:

Creeps (jungling) - Skeleton troll, Satyr, Healer, Ogre, Ursa
Creeps (post jungling) - Alpha wolf, centaur, ursa, satyr purger.

My rule of thumb for rushing items on heroes:

Midas - 5 min / 6 min at the most
BF - 12 min / 15 min at the most

Better alternatives if you didnt manage to make the deadline:

Maelstrom, Mekansm, Armlet.

Remarks: Always rushing aint the best, a good player is a versatile, flexible player.
Adjust according to the game.

If you jungle doom(i prefer laning), and your solo is in trouble, hard lane gets pushed, push the safe lane, get maelstorm not midas.

If the enemy team has an early game start , they start fighting, get Armlet instead of midas if your team lacks damage, or Mekansm if you lack teamfight power.

If you desperately need a stun get Centaur, if you need to deal damage get Ursa(magic damage) or Wolf(melee damage).

If you need to stop a slippery guy(weaver) , get skele troll, or for fast dudes(Bloodseeker) get Satyr purge guy.

Doom is one of the most versatile of heroes, do not waste his potential.

i usually go Basilus and then Midas before anything else.
Starting with tango + shield + quelling blade.

Its best to devour a Satyr for health regen first. If you cannot get one get a wolf. The extra damage will result in faster farming. Simply by another tango/salve then if you need to. The extra farming speed will make up for the cost.
After midas i usually get boots and shadow blade. This is usually the point where i leave jungle and start fully working with my team. But this heavily depends on how the game develops.

Also keep in mind that if you jungle from the beginning you should always keep an eye on the jungle-lane and tower. Help your teammates to defend it, if the tower is gone this will have a huge impact on your jungle performance because the tower provides some safety and vision.

Dont devour all the time in the beginning. Do it until you find the creep your looking for (Satyr/Wolf) and then delay it until lvl4 devour. You will need the mana mainly for healing with SE. Also you need to be careful what do devour, you can freely devour anything without skills without loosing yours (small centaur, lane creeps).