Theland; maybe start with the album Hot Rats (Peaches in Regalia is very accessible). Some sweet music much later like Watermelons in Easter Hay. Avoid The Torture Never Stops. And perhaps best avoid Titties and Beer.
I got into Captain Beefheart first, then my cousin, who was a complete muso, recommended The Mothers of Invention to me, and I got into them as a result. I'm not a massive fanboy, but I enjoy his stuff and consider myself a casual fan.
Yep, that's the classic. I'll be honest, I had a few chemicals running through my blood stream in my younger days. It loses a lot when you're not high :-D
I just re-viewed Stevie's Spanking live version. Steve clad in denim hot pants and leopard-skin top - straight from camp, pouting Spinal Tap era - Frank in Dervish pants with impassive face. You do need to be able to tap in time to appreciate this stuff.