I have worked at many beauty counters in DFS. All brands train staff in skincare. All brands make good products if you know what to pick.
Most everyone working in cosmetics wants to help. That’s why we go into these jobs. Sadly we do have a lot of pressure to sell, sell, sell, so a good place to start might be asserting what your budget is and asking the person to work within it.
I personally don’t think you should start with just foundation. Ask for a tailored skincare regimen and this will make any foundation work better. Brands are stingy with skincare samples now, but almost all of us have foundation samples so you can take your time finding foundation and work on balancing out your skin in the meantime.
Find someone nice who you can trust and talk openly with. I wouldn’t worry too much about which line you choose. I’ve worked for many lines and whoever I work for, that’s what I use and I haven’t got any real complaints.
I honesty believe a decent, consistent routine of properly cleansing and hydrating skin is the key. Cleanse, tone, serum, moisturizer, sunscreen. Skipping any of these is not advisable, though some people use an oil in place of serum or moisturizer.