To make things short to start, yes, get a SSD. In general, if your building a computer the ideal setup is get a SSD (around 120gb will be enough), although prices have dropped significantly. Ideally you will want to install your OS on the SSD and then setup a HDD for data (so that what be games, programs, etc.). Obviously if you want to install a lot of games on a SSD your going to burn your bank account quickly. I usually have the OS on the SSD and a few programs, I have a 128GB and have like 70GB left still (that should give you an idea). As far as boot times you will notice a significant difference. Think about it, HDD's are ancient now days, chips vs spinning platters!
To sum up, get an SSD! Not really worth putting games on, put them on a data drive (HDD).