There is no question that a primer does improve not only the application of makeup, but also the appearance and the durability of makeup, especially foundation/concealer/powder.
I am 40 years old but have a tendency to get greasy and everytime I use a primer, it is much worse! I have tried some of the best primers out there, bit for me, as long as I am using a good foundation, I am better off without one (though I know others rave about the results they get when they use them).
you should try Monistat anti-chaffing gel, it works great as a facial primer, everyone who has used it said its like Smashbox photofinish but much cheaper
I own smashbox primer but I usually don't use it unless it's a special occasion. I haven't really noticed any benefits to using it on myself. The only primers I do use everyday is on my eyelashes!