Jason90 :
You are right, I would focus on the main parts but also need to think about the bottleneck issues.
It is a tough decision for me as beginner to build a PC.
Do you think SSD is really needed?
I would use the desktop mainly for gaming.
The major bottle point is either CPU, or Video Card. To a lesser extent ram.
SSD is NOT essential for gaming. Having an SSD is a luxury that allows faster boot times and faster program launches. With gaming, what an SSD helps with is loading. So if your loading a level from an FPS to loading a zone from a teleport or whatever, it will be faster. More than likely, shaving off 5-30 seconds from a load screen you wouldn't care about. Once its loaded and in memory though, its on your ram and you are no longer bound by the limits of your mechanical HDD.
For an MMO, there is some benefit for an SSD as MMO's tend to be dynamic with the world loading around you as you go. Terrain, other player and character models may load faster if they were not already loaded into memory. So if there are a lot of people around you in Tera, say Nexus, and you are in a GvG, you probably wil lsee them on your minimap as a blip, but you wont see them. First person to see the other person gets the drop on them. It could mean 1-3 seconds in load time which would mean the world for serious pvp. But no, I don't feel even that much is necessary. It's a luxury to have, and not a requirement. You can add an SSD later if budget permits. With this pc, do you have an older pc you can take down and use for spare parts?
The big 4 thinks I feel you NEED to spend money on NOW, and spend it right, is CPU, Motherboard, PSU, and Ram. These are the more frequent causes of bottlenecks.
Pick the CPU you KNOW you want. Make sure the chip is unlocked so you can explore later overclocking.
Motherboard, like the CPU, it's to expensive to replace on a whim, so pick a good mobo. I would recomend a motherboard with the 990 chipset so you have SLI/Cross fire as an option in the future. Lower models may only allow Crossfire(and no SLI) or may not have the PCI-E slots needed to do a 2nd card if you choose in the future.
Memory, a moderate investment. Ideally think of how much ram you would need at most for your system. Try to get it on two sticks. Myself, I figured I would not likely use more than 16gb. So I picked a 2x8 Stick. That leaves 2 slots free which allows in some cases better overclocking stability with the IMC. Worst case scenario, if I do need more ram in the future, I still have two slots. Still, if budget is to tight to go with larger sticks, go with smaller capacity sticks.
PSU - Your PSU goes bad, your motherboard and hard drive are the most likely to die first. Second, you want to be sure it has the capacity you might need in the future if you do plan to overclock or add more hardware.
CPU Bottle Neck? You can overclock BUT
Overclocking you would want to wait until
1) You can afford better than stock cooling
2) have spare cash in case you royally screw up any overclocking attempts.
With your concerns with an HDD will be a bottle neck, yes an no. Yes it is a bottle neck, but not a necessity. You can buy an SSD later if it is an issue. SSD isn't cost effective as storage, so you would be need a mechanical HDD anyway. Get one good enough to use for your OS/Programs/Media. Later when you can afford an SSD, reinstall the OS and programs to the SSD.