First of all :

1. How much money do you have to spend on it? Does it include the screen, and hardware like keyboard, mouse, headset?

Then people will be able to help you more.

Look for a case with good build quality and cable management.

I'd highly suggest this case: http://m.newegg.com/Product/index?itemNumber=N82E16811119233
It's cheap, comes with 2 fans, and big enough to easily fit as much hardware as you'll need in there. I own it and it's awesome.

what x3 said

You can use www.pcpartpicker.com to compile your parts and it will tell you if the parts are compatible.

You can also use www.logicalincrements.com to see recommended parts, descriptions of each part, etc.

1) When looking for a case, you want to look for features (i.e. USB3, multiple fans, fan controllers, dust filters, etc.), size and what the case is compatible with: sizes are full tower (large, lots of room for expansion and the most features but the most expensive), mid tower (not as large and not as much room for expansion but affordable, imo mid towers are the best to go with) and micro ATX/mini ITX cases (small, hardly any room, probably should avoid), and airflow (does it have a lot of ventilation and fan mounts?)
2) Quality. Do NOT cheap out on the power supply, it's like the heart of your computer. If the power supply is too weak and can't supply enough or clean power to your components, your PC is gonna have a lot of problems. Look for 80+ bronze certified power supplies at least. Also, depending on what your budget is/what components you're getting, you'll want to look at how much power a PSU can give. E.g. if your PC has a quad core and a single medium level graphics card such as a Radeon 7850, you can get by with a 500W PSU. However, if you're going to have multiple graphics cards and a lot of overclocking, you're gonna want more Watts. General rule of thumb, buy a little bit more than what you need when it comes to a power supply. You can also look in to modular power supplies which allow you to remove cables you don't need to reduce clutter and have a tidier build, but it'll cost a bit more.
3) I've configured powerful AMD 6 core PCs at around £400 ($600-ish?) before which are more than adequate to run TF2 at max settings (trust me guys, AMD isn't that bad, especially because future games are looking to be more AMD optimised).
4) You want to invest the largest amount of money on your graphics card, followed closely by the processor. The graphics card is going to be doing most of the work when playing games, followed closely by the CPU, so make sure these 2 components are focused the most.
5) No. There's a lot when it comes to compatibility, for instance, you cant put an AMD CPU on an Intel motherboard, a full ATX motherboard wont fit inside an ITX case, etc. etc.

I could go in to more detail, but it'll take a while and I already know this is a tl;dr scenario, so add me on steam if you want more help: http://steamcommunity.com/id/larvalextract/

Overall, dont start building until you have a solid budget; it's not all about performance, it's about price/performance ratio (the best bang for your buck), and read as many reviews on separate components as possible! Hope this helps :)

1) when looking for a case what do I look for
Cable management, airflow, build quality, AESTHETICS.

2) same with the power supply
How ever much your system's components will be pulling, plus some headroom. Also, efficiency (80 plus, Bronze, Platinum, etc.)

3) what is the minimum I should waste to be a good pc that runs at a constant 60 fps in decent setting not maxed out but not low
For TF2, probably around $600 or so would be a safe bet. That being said, TF2 is not terribly demanding game, so if you plan to play other games at decent settings, I would aim for a budget of around $1000 at least.

4) what are the parts should i really invest more that others
Generally speaking, graphics card, processor, and power supply.

5) are all parts compatible or should I be looking for something specific
Not all parts are compatible, mainly processors and motherboards. You will have to find a motherboard that has a compatible "socket" with the processor (basically a motherboard that "is the same type" as the processor). For example, a socket 1155 processor, like the 3570k, will be only compatible with socket 1155 motherboards. Some cases will be only able to fit certain sizes of motherboards, so look out for that as well. Pretty much all "modern" motherboards will be able to run DDR3 RAM (the most common) and any up to date graphics card. On a related note, if you want your rig to look really pleasing, you might want to pick out components that have a similar colour scheme, but it's really not necessary if you just want performance.

Edit: ^ that guy went into a lot more detail, so listen to him.

thanks for the help here is the computer i build so far
http://pcpartpicker.com/p/1g4Rd
two more question
1) what optical drive should i get
2) is this a good build should I invest more on anything or less on something?

my range is between 700 to 900

Not familiar with optical drives, you should probably research a little.

You can get a PSU with much higher wattage for less than the PSU you chose. I would recommend the Corsair CX 600W.

What kind of games will you be playing?

There's very little difference between optical drives. If you want blu-ray get a blu-ray reader or burner. If you don't get a dvd drive. Something simple like this should work just fine

Also, that build looks solid for the price you're paying. It should do well in most games; fairly high settings at 1080p

You should be able to save a bit of money/upgrade some components if you check out http://www.reddit.com/r/buildapcsales

This build looks pretty good! Though I would go with a good 600W PSU just so you have the headroom should you want to upgrade in the future. Also, for just an extra $10 you could get an FX-8320 (8 cores instead of 6). In terms of optical drives, they're all pretty similar and really cheap, so you can get by with anything. The only real difference between them is some are blu-ray drives, which are pretty pointless anyway. Looking at this website, you can get an XFX Radeon HD 7870 for a little cheaper than the 7850 too.