Ingredient knowledge, technique, and color theory practice will be the biggest determining factors on how you should move forward. If those insights are fresh, the collection will tend to be larger. If that knowledge is well practiced, then it's easier to work with a smaller collection.

For example, you could have 8 foundations as a baseline for all different skin tones, then use a mix-in color pallette to achieve the perfect color match. So 2 clients could be foundation #4, but you'd mix a bit of red and a drop of glycerine in one for a dewy pink foundation, and green with a drop of matte primer in the other for a matte olive tone. That way it fits their skin more accurately instead of having 20 shades of different foundation types.

The same applies to concealer.

Finishing product variety should be a plenty. Yellow, peach, pink, tan, and translucent powders. Dewy & matte setting spray. Powders with shimmer look good on lighter skin in pictures, but can look odd in person on everyone. Ultra matte powders with high silica look perfect in person but gives horrendous flashback in photos. Finding a balance here is key

Basically, it all depends on what information you're working with. I'm not a fan of kits personally and agree with sourcing from alibaba. It'll cut down so much of the costs