Right. It only helps level loads for gaming, but it helps them a lot. If you need to store images/music/movies I'd get one of each. Otherwise, just the biggest SSD you can afford (well, up to 256GB - after that, I'd say you may be clinging to too many old games).
Do I need to put an SSD drive in my P.C along with a HDD or can i choose one, and if so which will be better for gaming?
NO. You do not need both drives, but many enjoy using both. An alternative for you if you have not already purchased is to buy a hybrid drive, and get the best of both worlds (to an extent) for much less money.
Game loading SSD vs HDD:
The difference isn't as much as you might think. I've seen actual reviews and tried it myself.
When a game first starts, there are sometimes cut scenes that can't be cancelled as well as the CPU and GPU sorting out the textures etc.
The games I tested varied from about 5% to 25% faster loading and that's comparing a hard drive to a 3xRAID0 (max 700MBytes/second).
It surprised me too.
The Windows experience is a different story. I had a failed SSD and temporarily went back to a 300GB Velociraptor. Fast, right? My system felt sluggish booting and opening apps despite my 8GB of RAM.
That Samsung 830 is a great SSD. It's not just about performance; many of the SSD's have short-term and long-term issues. I watched a blog with PC Perspective and they covered SSD's and the conclusion was: best is Intel/Samsung but Samsung 830 wins for price.
Guess your mileage may vary. I had a velociraptor and didn't get into BF3 maps until everyone else was already taking flags. Now I'm waiting on them. In Skyrim, sometimes the loading text that's about a sentence long disappear before I can read the whole thing. And my SSD is "old."
And the power on count is 729 so that fits rather well for a machine that is on for most of each day for approximately 2 years. One of my older machines has similar stats.
The statistic of note is down the list - E7 SSD life left = 100%
To answer the OP - yes, an SSD can make a game changing difference for some games. In EVE online entering space from a station leaves you vulnerable until your environment has loaded. That loading time is shorter from an SSD. Under certain game scenarios a 5 second difference can mean remaining intact or losing your ship and being in your pod.