Avoid the temptation to dump in a bunch of new stuff all at once. Taking a slow and easy approach here is much better than spending a couple of frustrating hours trying to resolve conflicts. Fonts belong in the Fonts folder. There are thousands of them of many different varieties. You will probably need only a handful unless you're doing desktop publishing or other fancy stuff.
Most applications now show what a font looks like in it's Font menu.
Another way to see them is with Key Caps from the Apple Menu. Open Key Caps and select the font you want. A sample shows up. To add fonts to your Mac, drag them onto the System Folder icon. Your Mac knows enough to put it in the proper place.