Newbie here , currently just lvl 15 jedi sentinel , duno what crew skill crafting and gathering should i train , can any of u give suggestion?

The crew skills you train will depend on what YOU want to craft.

 

For example, my Jedi Guardian has the crafting skill Synthweaving, which lets me make armor for other Jedi. The components I need to make Jedi armor come from the gathering skills of Archaeology and Underworld Trading.

 

My Commando has Armormech, which lets him make armor for non-force users. His gathering skills are Scavenging and Underworld Trading.

 

Other crafting skills need other gathering skills. I don't remember what it's called, but the skill to craft lightsaber crystals and parts uses components from Archaeology and Treasure Hunting.

 

Decide what you want to be able to craft then look at it's description in the Codex to see what gathering skills you'll need for it.

 

Also you'll want to be careful you don't go broke fast. Leveling your gathering skills costs alot of money if you level fast. Though it's kind of offset by the fact some of the nicer cfafted itemds can be sold for a good price.

Check this thread: http://www.swtor.com/community/showthread.php?t=530