Usually you don't need to copy either glide2x.ovl or glide2x.dll to the game's folder, but they won't do much harm if your files are compatible with your actual card. I mean, V1 files with V1 card, V2 files with V2 card, V3 files with V3 card, and so on. It seems pretty straightforward, but some people fail at following even the most basic and obvious recommendations.
Glide2x.ovl is a DOS-only driver for 3dfx cards. You will need it if you want to play Tomb Raider with the Voodoo Rush patch. It is usually located at C:\WINDOWS folder. If your path includes C:\WINDOWS, then you're done. If not, then you can copy your glide2x.ovl file to the game's folder.
Glide2x.dll is a windows-only driver for 3dfx cards. Tomb Raider is a DOS game, so you will never need any glide2x.dll file in pure DOS. And by never I do mean never. Period. Well, actually you may need glide2x.dll if you use some workaround to play Tomb Raider in Windows. More on this later.
Voodoo Graphics patch for Tomb Raider is a DOS executable file that directly accesses Voodoo1 for hardware acceleration. Therefore you should only use it if you have a Voodoo1, or maybe a Voodoo2 with heavily tweaked Glide environment variables. Any other card just won't work.
Voodoo Rush patch for Tomb Raider is a DOS executable file that uses glide2x.ovl driver for hardware acceleration. It should work with any valid glide2x.ovl for your 3dfx card, but unfortunately Tomb Raider tries to read the linear frame buffer when you press the ESC key, and the game crashes because it is unable to lock 3dfx frame buffer on any non-Rush 3dfx card.
What can you do then? Well, a PCI Voodoo3 won't work any better than an AGP Voodoo3, that's for sure. Same goes for Voodoo Banshee, Voodoo4 and Voodoo5. You'd better save your money for a Voodoo1, a Voodoo Rush or a Voodoo2. And the last one isn't even guaranteed to work.
Or, alternatively, you can use a Glide wrapper to run Tomb Raider. There are only two Glide wrappers for DOS games that we know of: Glidos and dgVoodoo. Try both and use whichever works best for you. Glide wrappers are Windows programs and will need both glide2x.ovl and glide2x.dll files, but not the 3dfx versions. They use wrapper libraries instead. Glide2x.ovl wrapper translates DOSGlide calls to WinGlide calls, and glide2x.dll wrapper translates WinGlide calls to either OpenGL or Direct3D calls. You won't need a real 3dfx card anymore, just an OpenGL or Direct3D compliant card. But actually only GeForce and Radeon cards are supported, just like with most other Windows games.
However, if you insist on playing Tomb Raider on your Voodoo3, there's still another Über trick you can also try: a half-only wrapper. You would install either Glidos or dgVoodoo wrapper, but replacing its glide2x.dll wrapper with a native 3dfx glide2x.dll library. This setup will only translate DOSGlide calls to WinGlide calls via glide2x.ovl, but WinGlide calls will run natively on your 3dfx card's glide2x.dll library. You may or may not suffer again the same crash when the game locks the frame buffer for read - it's been ages since I last did it. But you don't lose anything for trying.
And finally, the Super-Über trick: playing Tomb Raider inside Gulikoza's or Ykhwong's DosBox builds with Glide support. It is basically the same thing as using a DOSGlide wrapper, because those special DosBox builds also come with a glide2x.ovl file that internally translates DOSGlide calls to WinGlide calls. Then you can use any suitable glide2x.dll library, either a WinGlide wrapper or a native 3dfx driver. it has been reported to work with OpenGLide, psVoodoo (Glidos-compatible wrappers), dgVoodoo wrapper, Zeckensack's wrapper and 3dfx Voodoo2's native glide2x.dll library.
Expect this last option to be slower than the previous ones because Tomb Raider will run emulated inside DosBox, while the other workarounds allow it to run natively inside Virtual DOS machines. The performance hit on a low-end Pentium III will be noticeable. At least Glide calls will still run with hardware acceleration. There's an even slower but more compatible workaround: Kekko's full software implementation of Voodoo Graphics chipset. I can't recommend it because it's still under development and will be unplayable on a P3, but it will probably be the way to go in the future.