Im building a singlespeed with a 1982 Fuji Royale, now I want to build a rear wheel for it.
Im just not sure what parts I need, Hub, spokes an rim.

Do you have a suggestion for me, something not too expensive?

It's cheaper to buy a complete wheel, lots of places offer them. If you do want to build it yourself ( an honorable aim which I share), you'll need to give us a budget - you can build a reasonable wheel for less than the cost of a White Industries hub, and an absolute rubbish wheel for even less.

This bloke can sell you anything you want or build it for an extortionate ... er ... modest fee (seriously, he's a good bloke and active on the forum)

I was thinking about 250-300$ for all the parts. Can I put a freewheel on a track hub?

Yes

So Im going to start with the dura ace 7600 track hubs, now how can I calculate the spokes size I need ?

That depends on the rim you're using.

That's putting a lot into a very basic frame. I have a Fuji Royale and for the most part is built with used parts I already had. How about a humble Formula hub.

^ This. "Something not too expensive," will land you nowhere near relatively hgih-end Dura-Ace hubs. Not to mention the fact that you can snag yourself a Novatech or Formula for ~$40, and both of those offerings will have sealed bearings, unlike the DA.

Thats why im asking for help. A cheaper hub would probably be a good idea as it is my first time building a wheel. So wich one would be better? Novatech or formula?

You won't notice a difference, both are comparable in quality, and the quality is second to none, especially in terms of their price.

Probably a coin flip, but I really like Novatecs.

So of i buy a 36h bolt on novatec rear track hub, now i need a rim and 36 spokes, any suggestions?

I would like a silver rim, strong enough to ride it everyday.

Cheapest option if you want to do it to say you did:

1) Buy a complete [machine built] wheel.
2) Take it down to bare hub, a bar rim and a pile of spokes and nippes.
3) Buy new rim tape.
4) Rebuild.
5) You built a wheel!

e: echoing the statements about frame quality. That might be designed aroun 27" wheels. Heck, it might even have 27" wheels. It's not a huge thing, but if you're like me, it'll get your OCD to flare up if you build a 700c wheel for the back while the front was a 27" wheel.

I dont want to say i did it, i want to learn how to do it. I just want to start with parts that fit together.. And yes the original wheels are 27''s. Can i fit 700 a pair of 700s on it?

You can look up Sun CR-18 or M13 rims. Cheap and good quality, good beginner rims.

This site has a good data base of hubs and rims. https://leonard.io/edd/ You can also learn to measure the parts to double check.

IthaDan's suggestion is a great one: buy a complete wheel - hell, get a 27" wheel if that's what your frame is made for - and then completely disassemble it. This way you absolutely know that all the parts will be the correct sizes, etc. because it already came put together. So there is no guesswork for you on the part list. Then, when you rebuild the wheel you will have lots to learn about lacing spokes, trueing a wheel, etc. You absolutely will learn about wheel building this way.

Thats exactly what i needed, thanks a lot.