Oblivion is such a gem. A goofy, janky gem. Definitely one of a kind.
For modding, I recommend using Nexus Vortex as a tool... reason being - it is stable, well-developed, and automates stuff that takes much more time and learning using the tools guides will mention to you. The classic tools have some advantages, but unless you have very specific, technical goals, Vortex is basically plug and play, with a much more user-friendly interface.
The first mod I recommend doesn't require Vortex, though. It's the 4GB memory patch:
https://www.nexusmods.com/oblivion/mods/45576?tab=description
Just follow the directions for that one, it helps with performance and stability on modern systems. Since the game is 32 bit, 4gb is alll you can use, but that's still far better than two!
The other would be the unofficial patch. This is the base version, with additional patches for the DLCs also linked on the page.
https://www.nexusmods.com/oblivion/mods/5296?tab=description
Won't hurt your experience at all, just spares some future pains. I do recommend you just use Vortex to install that one. As part of setting Vortex up, it will prepare everything and update the plugin list for the patch mods on its own. You can drag and drop the files in, click install, and just enable the mods. People will recommend all sorts of ways of managing and installing mods, but honestly, they have a different concept of time investment. They'll sit there and learn those tools, go through a lot of bullshit to work more directly. Vortex makes it hands off and 9 times out of 10, kind of just works. So if you ever do want to mod more, you can start installing them and trying them out through that. It's basically a safe sandbox that can project mod setups onto your game folder. Screw up, you can disable everything with one click and have a clean game folder. Nexus also has a 'collections' feature, where experienced modders can upload their setups, and you can download the collection file, which Vortex will use to pull the whole setup into your game folder. I've never used them, but it may be worth checking out if you just wanna try out a modded experience, done by someone who's already put in the time and ready for you to just play.
That said, I might actually recommend you play it largely un-modded, maybe browse around and take some visual upgrades you like. But for someone not acquainted with ES, the vanilla experience is actually pretty worth checking out. Mod it if you get bored.
I play games to see how beautiful they're made, my aim is not to be challenged or do combat. I found its faster to get feathers from Jobberknoll by brushing it. It's a colorful bird that its name reminds of John Knoll the creator of Photoshop. 
