I don't know if I could ever recommend that someone play oblivion in vanilla form. At the very least pick up OOO (oscuro's oblivion overhaul). That is THE must have mod for a lot of people. I would also highly recommend Qarl's texture pack. There are a bunch of others that I would argue highly enhance the game, but there are already plenty of lists out there.
If you do feel like going with 5+ mods, I'd start to look into OBMM (oblivion mod manager) which allows you to enable/disable mods with 1 click and check for/fix conflicts very easily. That might bring you into the realm of needing to consult google. I'd start with a youtube tutorial on OBMM.
The problem with Visual enhancers in Oblivion is that they can make the game crash if it exceeds 2GB in memory usage. Normally vanilla Oblivion won't even get close but when you start to add mods they get more and more demanding. I myself use the 4GB patch and the Oblivion Stutter to double the limited and for my mods it does fine.