Expensive foundation looks terrible - help needed!

[Ohanarama]

I have bad skin - rosacea and large pores and prone to spots - but that is a whole other thread!
Anyway I've recently bought various products to try and improve my skin and I'm getting quite good results so I googled what foundation to wear to provide good coverage without upsetting my skin. The foundation most recommended on the reviews I read was Estee Lauder double wear.
Last weekend I braved going to the make up counter (because of having problem skin I'm always nervous of such places!) and the assistant took off my make up and applied the foundation and it looked AMAZING! She only used a tiny amount of concealer under my eyes, whereas I always smother loads of it on.
Anyway, I obviously bought some (£29.50) but it looks terrible when I apply it, it cakes around my nose and in my pores, and my face goes quite greasy and patchy after a few hours. It looks worse than my previous cheap (maybelline) foundation!
The counter lady did apply it with a brush, whereas I use fingers, would that have made such a difference? Or could it be my moisturiser causing the problem? I need advice please, not just because of the wasted money but also because I'm so disappointed, I want my skin to look lovely again.

I have similar skin, large crater pores, acne scars, rosacea, flaky skin the lot.

I hate double wear, looks terrible, highlights every pore, cakes, flakes just terrible.

Primer helps but can make my skin worse with constant use, dries out my skin, stings.
Smashbox the blue hydrating one works well.

So far tinted moisturiser works best, evens out some redness and doesn't pool in my crater pores.
Not heavy coverage but makes me look a bit more polished.
Clarins hydra tinted cover works well.
Can't wait yo try the new bare minerals.

Well I found out what they used at the make up counter. ..a primer type product called "Idealist" and a cream called "Daywear". Have got samples but they cost £98 together so I can't afford them even if they are bloody wonderful!
Also bought a foundation brush and I made an impulse buy of some L'Oréal mattifying primer. Have given both a quick try just using my old foundation and have got quite good results, think it may be the brush which has made the most difference, I can't believe I've never used one before!

Also use very little, you can always add more. But honestly a pea sized amount is more than enough. x

It's definitely worth trying Lanacane as a primer. It's about 6.80 and great for everyday use. Some of the standard primers are fine, granted, but I honestly can't see a real difference myself and I guess Lanacane is at least one third of the price of most primers. I get through more tubes of primer than foundation so find it this a good saving.