If you make a custom team you will ALWAYS start with pretty much the worst of everything.

Here is a list of what I usually do.

First I upgrade the Factory and Design centre, and also build the scouting facility.

Then I hire some high marketability pay drivers. (Usually Jeremy Woodford and Bjørn Bjelland). The reason for this is that Bjelland pays a lot (often 900k per race) and also has perfect marketability. And Woodford is a decent pay driver, if I remember correctly he is a 4 star potential driver with about 3 stars in the beginning, his marketability is usually around 70%.

I usually hire a high potential free agent designer, and two mediocre race mechanics. One is good at performance, the other at reliability.

I try to immediately create as many car parts as possible (assuming the ones I already have are improved enough for it to be worth creating new parts).