Hi, new here and relatively new to OB (about 25 hours in). Just wondering what level I should be at to competently attempt the OB Gate at Kvatch? I attempted it straightaway and, of course, got my ass kicked. I am now at level 8 and thoroughly enjoying some adventuring/leveling up in the Shivering Isles...actually don't even want to leave there, but want to get back to the main quest. Any suggestions on level and/or weaponry etc...? Thanks.

Everything is leveled with the player in Oblivion, so the gate (or any of the quests for that matter) aren't going to get any easier as you level up.

EDIT: Most of the time in Oblivion, if I was having a hard time, that usually meant I had "old" gear. Do some dungeons and get geared with the best loot you find and then try again.

The two schools of thought are:
Do it early as you can, as it leads directly to going into Kvatch with Savlian Matius and his crew, who don't level up as well as the monsters do.
Do it later, as your own level outpaces the enemies, and the Kvatch guards are expendable, in order to get a better Sigil Stone.

The usual advice for Oblivion worlds is "resist fire, deal shock damage". Most of the enemies will throw fire at you, and most are weak to shock. That won't be true at higher levels, but by then you won't need advice on how to fight. Any general combat rules for your character build still apply, and the world itself will contain both open and tight areas to fight in, so you need multiple strategies.

I personally like to go in early to minimise my followers death in the retaking of Kvatch. Either way, early or late, you may still be in for a fight but level 8 should go much better than when you went in before. Grab some good weapons/gear and/or arm your best spells healing potions & spells and go for it

I agree with all the advice. Higher level means better sigil stones but dead helpers.

Another factor is your character's own skill set. Some characters see differing difficulty curves. Warriors start easy and gradually get a bit harder to play if they don’t begin to branch out. Pure mages are hell to start, but by higher levels are unstoppable. Pure archers without some magic or blade to help are always going to be a challenge during the battle for Kvatch.

Thanks for the information all. If I can ever peel myself away from the SI long enough to progress through the main quest, I'll take all you've said to heart.

My characters usually wait until they are level 17+ before they go to Kvatch. That way you get a Transcendent Sigil Stone with the max enchantments.