First off, I'd suggest figuring out what you would like to achieve with the makeup - do you want to hide dark circles, bags, even out your skin tone, get some colour on your lips/eyes, look more awake or something else?
Do you want an everyday look or a party look or an everyday look that you can make into a party look without having to buy loads of extra stuff?
How easy would you like it to be to apply?
When you go to a shop or counter without any ideas of what you're looking for, it's very easy to buy way too much and to get products that aren't really what you really wanted.
So if you have an idea of what you want to do with the makeup, you can describe this to the sales person who can suggest products for you.
What is your budget and do you have any makeup brushes already?
If you need brushes, I'd suggest a foundation brush (if going for a liquid foundation, Real Techniques Expert Face Brush is awesome), a Mac 217 eye shadow brush and a blusher brush. You can always buy more later.
I'd suggest getting a light to medium coverage foundation. Ask for samples so you can try it at home and so you can see how it looks on your skin during the day. Mac do not give out samples, but they will apply it on your face for you so you can test it like that. I like Estee Lauder Double Wear Light, Laura Mercier oilfree tinted moisturiser and Diorskin Nude. I have oily, dehydrated skin, oily mainly in the T-zone and find that these foundations work really well for me.
A pressed powder is nice for touchups, especially if you have oily/combination skin. I like Mac Select Sheer Pressed and Mac Mineralize Skinfinish Natural. The first comes with a powder puff, the other one I'm not sure about as they've recently changed the packaging.
A good mascara - they come in all price ranges.
A blusher - I'd suggest asking for a recommendation at the counter. Mac has a great selection and they really give good advice on which colours are good.
A lip product if you want it - whatever you like. Red lipstick, berry, neutral, gloss, matte lipstick, stain or anything else.
If you just want to try different things, you could start with cheaper brands and when you find the type of colour you like, you can then buy more expensive products if you want.
Revlon Colorburst Matte Balms are matte lipsticks, I really like them and feel they compare well to more expensive brands.
I don't know what kind of eyeshadow colours you like, but I would suggest having a look at a Paint Pot (cream eyeshadow) from Mac called Indianwood. It's a gorgeous shimmery bronze that can be worn as a light wash of colour or a bit more for a party like look. It looks great just with mascara and a neutral lip colour but also amazing with eyeliner and red lipstick.
For cheaper blushers and eyeshadows, Sleek are very good, but they are very pigmented, so you have to use a very light hand when applying.