I started Billi out with sleeveless shirts to get her used to having clothes put on and off. At first she seemed annoyed, but she got distracted quickly. Now she can wear longer sleeves fine. She's so tiny that a lot of jammies are a big big on her, but I had a pair fitted for her (had the cuffs tightened so they'd stay on) and she doesn't mind them now. Still working on getting her into wearing costumes- they are kinda bulky and I'm sure my furious giggling doesn't help matters
I agree with those who suggest distracting Gizmo so he forgets he has anything on him. If it's not too tight, or too loose, he'll get used to it quicker and more likely he'll like it.