I've used Thin Lizzy for quite a while now and it took me a wee while to finally figure out what works for me.
I'm fairly sure that they've changed the formulation or there is some variation in the lighter shade as I used to be able to use it as the foundation that they do in the ad. If I try that now, I just look orange. The way I use it now is as a light "dusting/buffing" (almost, can't really think of the best way to describe it) over a good primer on my "lazy" makeup days. I'll use it a bronzer/contour on my days when I get up early enough to do a proper full face of makeup (primer, concealer, liquid foundation, bronzer, blusher etc. etc.) The one thing to remember is that less is most DEFINITELY more. There is definitely a very fine line between looking like you've got a bit of colour and looking like a cheeto with Thin Lizzy. If possible, apply when you've got access to some natural lighting. I can't tell you the amount of times when I've looked awesome in my bathroom mirror and I look like an orange outside. *sadface*
The lipgloss is a fairly horrible consistency. It's thick, goopy and generally unpleasant to put on. Don't even think about having your hair down around your face if you have the lipgloss on otherwise you'll be pulling hair out of your mouth for hours.
The eyeliner really isn't too bad. It smudges very easily so you can make quite a good smoky eye but you need a way to get it set properly (which I haven't yet figured out or learnt how to do).
I use thin lizzy's occasionally for quick & light makeup when i can't be bothered doing a proper job. I find It good for a bit of color and dimension applied over a BB cream to the cheek bones & eye lids and finishing with a light coat of mascara for a minimalist look. I don't love it i don't hate it and probably wouldn't buy it again, the only reason i have it now is because it was given to me. This product is way overrated, made out to be a miracle worker in advertising but really it's just okay.
Tips: Apply sparingly