I am making a Thief/Assassin-like character, and I am honestly not sure about these perks, but I made a build:

http://skyrimcalculator.com/197091

If anyone could give me some pointers, tell me what's useless/pointless that'd be great. There's 1 point remaining because I have no idea where to spend that. I wanted "Extra Pockets" from the Pickpocket perks but I was not sure if it would be worth it.

As for the perks in One handed, I'm not sure if they even affect daggers, but if they do I assume they are quite useful. I also left out certain perks in some trees because I felt they were pointless but I could be wrong...

Thanks in advance!

EDIT: Also, as for stats I gain when I level, I was thinking of going HP first, then Stamina, then HP again and so on, I assume I don't need too much HP so this should be fine?

I found 5 points (+ 1 of yours) who you can invest in Illusion, which is a nice addition for thiefs.
First point is Bribery, If you're gonna take Unbreakable for lockpicking, I think it's a waste to spend one point to Master locks.
Steady Hand, you do not need 2x points in it, because you will be based both on archery and one-handed, so basicly archery should be only for oppener when you have many targets. While the target is idle, you won't need slow-mo. If you didn't have one-handed and you were based only on archery, then Steady Hand is good perk, but in this case you can drop it with no regrets.
Agile defender is okay with 4/5 to hit cap, if you're gonna use smithing (which obviously you are), so you can upgrade your armor above the cap even with 4/5.

In this case, you'd have 6 points to spend, and I'd go for Illusion at your place. From Novice Illusion to Master of the Mind, just follow the central tree perk, and go for it. It's very handy. And you will have one more left, use it for Illusion Dual Casting.
Ofcourse this is my point of view, feel free to look for more ideas

Lockpicking - there is no point getting the unbreakable and master perk, either one or the other (id suggest unbreakable)

Light Armor - If you are perking smithing and alchemy, putting perks here seem redundant as you can get your armor rating high enough with just smithing and alchemy; plus alot of them only apply when you wear it on all body parts; my thief/assassins always wore hoods.

Sneak - putting all 5/5 in the stealth perk is overkill, you can get away with just one

Speech - id suggest filling up the left side or at least to merchant so you can sell anytype of item to any merchant. Usefull when you are an alchemest to be able to sell high value potions to anyone.

Pickpocket - for the assassin/thief i am playing now I filled up this tree except for key master and perfect touch. The poisoned perk is very handy for silent kills and pickpocketing npcs weapons first and then going hand to hand or hand to dagger with them is fun. Be careful as they will run to the nearest chest or table and grab an available weapon.

One handed - the perks do apply to daggers, fortified one-handed enchantments don't. I have the same perks for my assassin except I added the savage strike perk. Just someting about decapitating someone with just a dagger screams master assassin. Edit: picking both dual flurry is a bit unneccessary if you plan to dual weild daggers as they swing pretty fast. Using one perk to increase the speed by 10% is a bit of a waste, better to use it in the pickpocket tree.

Archery - the bullseye perk is a bit useless as you can enchant or buy a paralyze bow that works at a much higher success rate, also you can use paralyze potions. This perk still may be glitched. Personally I never used the slow time perks. They are helpful but I like to just zoom in without slowing time. Seems like more of a perk for an offensive bowman then a stealth bowman. Getting both my be a bit much, one would do.

Just an additional note, when you first go into the rat-way make sure you loot and disenchant the gloves of the pugilst (found on some guy with fist in his name). These are the only fortify unarmed damage item in the game. Then you can enchant gauntlets etc with fortified unarmed and unarmed has some great kill cams. I used the fortify restoration glitch to make some powerful gauntlets for my assassin once he became a high level assassin.

Edit - I agree with bricstix, I added illusion to my assassin and it is alot of fun. Invisibility is extremly valuable expecially used with the shadow warrior perk, you can regain hidden status when you are discovered. Frezy is a ton of fun and calm is a great defensive skill.

I don't plan on using -any- magic on this character, so I won't be putting points in Illusion. Would you recommend putting 3 points in Pickpocket just for the Extra pockets perk? Should I put more points in One handed or are the ones I already chose the only ones that will affect dagger? Is any of the Lockpicking perks I left out any good, or did I guess right by not chosing them?

Oh and thanks for the reply so far.

EDIT: Oh, seems like you wrote your post while I did jcote23. I'll make some changes to my build based on your and bricstix's replies and post it soon, thanks!

EDIT2: Okay, I changed it to this http://skyrimcalculator.com/197126

With this there's 4 points to spare but I am not sure where to spend them. I can see the usefulness in Invisibility, but even with the Expert perk it'll still cost 164 magicka to cast.. and I don't plan to spend any points in Magicka, so I won't be able to even cast it.

I could spend 3 points to get Extra Pockets (100 carry weight) and the last point in Alchemy to get Snakeblood (50% resistance to poison) as I am already a Redguard that'll give me immunity to poisons, although I'm not sure how often you even encounter poisons in the game..or I could spend that last point to get "Fence" from Speech. At least I'm not sure if I want to remove any more points than I already have from this build.

I'd put the 4 points in pickpocket to get the extra pockets and the poisioned perk. If not the poisioned perk I would put the extra perk into fence rather then snakeblood as you are correct you dont encounter poisions too often, mostly from chrarus and spiders. Being able to sell your stolen goods to anyone you invest in is handy even though you will get more fences once you complete the rebuilding the thieves guild quests.

Personally I would knock down the stealth 5/5 to finish off the speech left side.

The Poisoned perk in Pickpocket, does it make people aware of my presence when they take damage from it? If so I'd rather not use it honestly. I put 3 points in Pickpocket to get Extra pockets at least.

Whether or not I use 1 point from stealth to get Master trader I'll consider when I get higher level.. so far on my warrior I've rarely had a lot of issues with running out of places to sell. Expecially in places like Whiterun that has 4 vendors that can buy armor and weapon (not including the trader) 1 that can buy everything (the trader ) 1 for potions and ingredients and 2 for magical items (court wizard and trader) if any of these run out I don't mind going to another town to sell really.

Also I heard you get a lockpick at some point that can not break, so wouldn't it be smarter to just get the Master Locks perk instead of Unbreakable?

As for stats, you think 1/1 Stam/hp is fine or should I go 2/1 hp/stam?