Hello , im considering making a thief since mage svcks , and i need basic tips like which perks should i go to , stamina/magicka/health , and what city is the best for thief quests.. ty

For Attributes: I would up Stamina and Health at close to a 1/1 manor and put points into Magicka on occasion if you use it (I use conjuration on occasion when stealth fails.). For Perks I recommend focusing on archery (all perks except steady hand.), Sneak (at least get up to Muffled Movement and Deadly Aim, Assassin's blade is nice but not really needed.) You don't really have to perk up lockpicking too much unless you want to finish the thieves' guild's final core quest. Pick Pocketing isn't really needed (on one Thieves' Guild Quest needs you to do it and it's not hard, just save before you try.) One handed will be the melee skill of choice and I recommend to focus on swords for the critical hit.

Riften has the Thieves' Guild and is the best city to quest in. You get some really great rewards from it's questlines.

tnx a lot man , so i should stick to swords , not dagger? o.o

Well, it's obviously down to personal preference to some extent, but I have my stealth/thief/assassin character set up roughly like this:

Main skills

Sneak
Archery

Main weapon - best dagger I can get hold of. Note that you get huge dagger damage bonuses from Sneak skill/perk tree. One-handed skill isn't necesarily useful (as far as perks are concerned) for daggers.

There are two factions/guilds that work well with a stealthy character. I'm not sure how much of a spoiler that would be, so I'm not going to name them, or say how to join them.

I don't use magic on my thief/assassin, or do any enchanting or smithing. That's a deliberate decision. If you want a more powerful character, those skills will definitely help but they don't feel like thief skills to me.

As I said, that's my personal preference. I'm sure others will respond differently, but that's what Skyrim is all about - building a personalised character.

No. If you use the dark brotherhood Shrouded Gloves and have assassin's blade then you can do X30 damage to unsuspecting victims. My assassin/thief has 100 sneak and can hide mid combat. I kill bosses with one hit by systematically deleting all of their bodyguards from the room and then slitting their throats. You DO want assassin's blade and you DO want more perks in sneak IF you can afford to spare them. Remember, the lockpicking perks are almost useless. I have around a 75 in lockpicking and can pick master locks just fine and haven't put a single point in there.

Well You probably should Carry both, Assassin's Blade isn't too much, it's one perk point, I prefer sniping on my thief so I don't use my dagger too much but it's not heavy and great for Melee stealth kills when you can make them work.