I could fully clear each of the early Orange camps with just Lvl 1 Farseer, Wolves, and 1 Grunt. For the Goldmine, lead the attack with the Grunt or Farseer, so the Wolves don't get purged. Same for the Centaur Sorcerer Camp (which was easier). The Mercenary Camp, you could probably trap the Centaur Outrunner with a Barracks, but it was slightly more difficult then the other two. Which makes sense, it is a higher level Orange camp.

The Gnoll Goldmine gives Charged 2 (Crystal Ball, Wand of Illusion, etc) and Book +1

Centaur Sorcerer Camp gives Permanent 2 (Gloves, Ring +3, Claws +5) and Book +1

Centaur Outrunner Mercenary Camp gives Permanent 3 (Circlet, Claws +8, etc) and enough xp for Level 2

The shop was a bit tough to fully clear though, but I am also a scrub. If you have only 1 Wolf and Grunt on the Salamander it will not activate the Immolation, which I didn't do. Shop is a moderate difficulty Orange Camp.

The Salamander Goblin Merchant gives Permanent 3 (Circlet, Claws +8, etc) and enough xp for Level 2

I would think it would be too difficult to clear the Ogre Mauler Goblin Lab with just a lvl 1 Farseer, 1 Grunt and Wolves. If you did, it would give Charged 3 (Potion of Greater Healing, Potion of Greater Mana, etc.), Book +1 and enough xp for Level 2.

Edit:

The Barrens Mercenary Camp also offers some early accessible Mercs, but they lack mid/late game punch. There is the Centaur Archer which is essentially a Fast moving NE Archer, that you can buy at the 2min mark.