Mr Will says this is a pretty damn good harness:
"...for anyone looking for an inexpensive harness to learn with, the Tantus Vibrating Velvet Harness is probably the way to go."

Tantus’ Vibrating Harness is the perfect accessory for beginners. The soft velvet material is soothing and sensual on the body, while the adjustable two-strap design allows for a customized fit providing maximum comfort and satisfaction.
The Vibrating Harness also comes with a removable 1.5" O-ring, accommodating different size toys for different levels of experience, and a waterproof One Touch Bullet Vibe for extra stimulation.
The Vibe Harness can also be worn comfortably over non-erect penis & scrotum. Users suggest wearing underwear beneath the harness to keep everything in place during use.
Vibrator: Single Speed Removable Waterproof Bullet Vibe, Uses 1 x 1.5 V N Type Battery
Dangerous Lilly recommends this inexpensive and versatile harness to beginners:
"Everybody needs to start somewhere; you need to be sure that both you and your partner are into, and able to incorporate, strap-on harness play before you shell out the big bucks. "
Have different dildos you want to try in a harness?
Six piece set of O-rings to secure your toy in any harness