On equipping cross-class abilities, take a look at this page. You just check out the left hand side of the Actions menu, under "Additional Actions", click on the Conjurer Icon (it looks like a branch with leaves). This will bring up the Conjurer actions list, and you just pick Cure or whatever other abilities you want from Conjurer. Keep in mind there are 2 restrictions: You can only equip abilities that fit your Class, so Gladiator can only use things from Conjurer that includes "Requires: Disciples of War" in its description. The 2nd restriction is that you are limited in the amount of cross-class abilities you can use. It's the number to the right of "Additional Actions". You start off with only 1 cross-class slot but as you level up you gain more.

For low-level equipment, there are Newbie NPCs in the adventurer's guilds that sell level 1 to early 20's items that are extremely inexpensive. If you have trouble finding them they are marked on the map.

Lastly, if you want to craft armor for Paladin/Gladiator, of course you would need to level Armorer =P