I'm terrible at modding this game. In Morrowind I could use a huge mod pack, Skyrim is easy to mod, but Oblivion... I had several tries but I never got it to work properly. Now I decided to try again.

I managed to install Unofficial Patches, Oscuros Oblivion Overhaul and Darnified Ui using OMM and so far it was successful as the game at least worked after leaving the sewers (last time I couldn't even launch the game after installing some mods).

Then my goal was to get it working with texture mods. I downloaded those mentioned here: http://forums.nexusmods.com/index.php?/topic/1483493-an-up-to-date-mod-list-created-2014-03-08/ since they were supposed to work without conflicts. I've been unpacking and copying them to data folder one by one, checking if the game still launches and all, and after were installed (except Oblivion Character Overhaul as it looked more complicated) I started checking how everything works. The game launched and new flora looked really good but unfortunately I already got a problem not close from the sewers - there is a WTF Missing Mesh star thing floating near the water. And I supposed there will be more in different locations...

Any idea what can I do now? I guess there is nothing more possible than starting again from scratch but what can I do different this time - I downloaded only the simplest moddest listed and it something has already gone wrong.

Try using Wrye Bash instead of OMM (which is a bit old) - much easier to diagnose problems, especially matters of install order as opposed to load order (it sounds like you're installing the texture packs manually). It's also a very good idea to use BOSS to sort out your load order if you haven't already.