Im wondering is there anywhere a list of essential mods for Oblivion for me to download and install ?

Also Im wondering is FCOM lore friendly, because I don't want to have mods which break the lore ?

And also is trhere anywhere a mod which fixes level scaling system so there wont be Marauders and Bandits in Daedric and Glass Armor ?

Essential mods? This falls under the category of opinion, in my opinion. The only really "essential" ones I can think of are the Unofficial Oblivion Patch (which is at www.Nexusmods.com ... you'll have to register at Nexus if you haven't already), and also some sort of mod manager, assuming you begin using lots and lots of mods, you'll need to organize these somehow. Nexus has its own mod manager if your mod list is light. I prefer Oblivion Mod Manger Extended, (OBMME) which is also at Nexus.

Unofficial Oblivion Patch (UOP) fixes a lot of things which Bethesda never got around to fixing.

I have heard good things about FCOM, but I don't use it personally. Whether or not it's lore-friendly? Not sure, but it sounds like it is, according to what friends have described.

Yes, there are lots of mods that do this. I believe FCOM will "fix" this, but I prefer http://www.nexusmods.com/oblivion/mods/37217/? which is much simpler to use. BOO has four different esps, one of them "fixes" this issue with glass / daedric armor. Anotehr one makes special loot in containers much more rare. I don't use the other two

I agree completely with RG3. I don't believe in "one-size-fits-all" so-called "essential mods. Everyone has their own private list of mods that are "essential only to them. My list is different than someone else's and their list is different than mine.

With that said, you can take a look at the Nexus' list of most endorsed mods of all time to get you started: http://www.nexusmods.com/oblivion/mods/topalltime/?advlt=0

No, there is no "essential list". However, I recommend downloading and installing the official patch, OBSE, Wrye Bash, BOSS, OBMM, a Darnified UI of choice, and the unofficial patches for whatever official things you have installed (Oblivion, SI, DLC). Elys Universal Silent Voice is a must when using a lot of mods. Oblivion Stutter Remover can help with stability.

Beyond that, I suggest you have a look at TIE, which is perhaps the smallest "overhaul", and is also fine with regards to lore. And yes, it fixes level scaling, as well as making the game harder in general, and does many other things besides. Cobl is a nice mod in general, and in particular offers a lot lore-wise. Maybe have a look at Cliffworm's mods (the "Oblivifall" range) too. The Oblivion Content Restoration Project looks promising too. Enhanced Economy is almost required, I think.

Unique Landscapes is great, and either Better Cities or Open Cities Reborn will do a lot to improve the cities - OCR brings.them closer to how they were precented in images early on, in case that's of interest. There are other city mods as well, which might appeal more. And a number of modders have made village/town mods - take your pick there, if you like.

I'm partial to Supreme Magicka, as the magic system as it stands needs work, in my opinion - there are plenty of alternative approaches, however. Sneaking Detection Recalibrated is the king or queen of stealth mods, and well worth it. Alternative Beginnings is rather nice, assuming you have ever played Oblivion before. Weather - All Natural really helps with lighting and atmosphere, both indoors and out.

Anything more specific in your wants and "not wants" would help greatly. What is it that matters, doesn't matter, you would like, wouldn't like, are interested in, are not interested in ... ?

edit: As far as graphics go, it's highly subjective, but I think almost all games would benefit from both RAEVWD and Animated Windows and Lighting.System. Make sure to download TES4LODGen if you install those mods, and run it after you've installed all mods, and made a Bashed Patch. On that note, I suggest running TES4ll to generate landscape meshes, normal maps and textures (by default, it takes into account all the mods you have installed).