Somewhere early in SOU I remembered getting a helmet wearable only by paladin, and a suit of armour and shield together as a reward. I had forgotten where I got them. Can anyone helps? Thanks in advance!

In the elven crypt, accessible from the third map you visit (the one where you hunt the Shadow Hart).

So if I'm a cleric now, what should I get? Only a cloak or is there something I forgotten to do so that I can get more than that? Thanks in advance!

I believe if you are not a Paladin, you don't get access to that part of the map, so you get nothing.

Oh... Does that mean I will not get rewards specially meant for cleric?

Well, you do get access to that part of the map, but on completion you only get the cloak, whatever class you are, unless you are a Paladin, then you also get the full armor set.

What other class-specific equipment was there in SoU? I remember a manticore cloak wearable by only druids and rangers, and not that much else... Ok, harps and lutes not included.

There's a lot of bard/druid-specific stuff, but not really much else in terms of class restrictions.

That paladin gear is pretty good too...I wore the armor and helm throughout the game...I traded in the shield for a better one at some point...