Hi Sunny, that's a great question. Confidence feels really important in these situations. I think first I would say, in my work with Best Thing or in making comedic videos I am/was confident I could deliver -- on a subject I feel drawn to or passionate about. I was also confident that I had a unique voice to bring to the table -- not unlike the short film that @Bri_Castellini just made about asexuality Ace and Anxious -- when I watched it I learned something new. She has a unique voice.
Asking people for money: it's good to remember the amount of money you're asking for is probably pretty small in the scheme of things. When Dove makes a commercial it costs hundreds of thousands of dollars -- if you want to do a branding deal with them and you need $5000 or $10,000 that's pocket change to them!
Dress for the job you want (did you see this on twitter yesterday about Melania -- made me laugh out loud) But that's really helpful to me, to feel great about what I'm wearing in a meeting. Rent the Runway has everyday work clothes now and sometimes I rent an outfit (a stylist can help you btw)!