hun, your hourly rate is what you want to earn in general
so say you wanted to earn £10 an hour take £10 then add product costs etc to that , this is for EVERY treatment you do, every business has to have an hourly rate that covers the cost of staff, products everything. if you had a shop your hourly rate would include rent, rates, gas electric and all staff etc so that you knew how much it was just to open up shop and turn the lights on. i hope that makes sense!
lets say im going to do a party for an hour - me personally i would charge around £50 and they could have as many tattoos as they wanted, i would probably remove my most popular glitter colours for this and prob only do small tattoos for it to be worth my while, i generally leave the larger tattoos for events where people pay per tattoo
each kit that you buy contains enough product to do however many tattoos is in the kit so like i said before divide cost of kit by how many tattoos are in kit, if there is any glitter or glue left out of the kit that is a bonus!
if you are applying glue thinly then maybe you are brushing glitter too hard and removing some of the glue in the process? just practise hun if you can....as my boys are older i couldnt practise much andjust through myself in to an event xx