i've basically been throwing the highest rating ship from tier list together for fleet building and i hear w14 and 15 require some actual team building so i need some pointers 
#help me build some fleet for w14 and 15
celest dust
supple root
give these a read
Chapter 14 Guide - https://suchiguma.github.io/guides/chapter-14-brief/
Chapter 15 Guide - https://suchiguma.github.io/guides/chapter-15
w14 you can give these fleets a try
FDG unicorn indep
eldridge sandiego z52
musashi shinano amagi
agir plymouth anchorage
supple root
the gearing example
may differ depending on what you have, but the important part to take note about is the CL gun on your BB, very important for killing the suicide boats, and desyncing your CV airstrikes, as well as having torpedo bulge on Agir because she's Heavy armour and thus takes more damage from torpedo
if you have extra plygun that would be even better to put on your BB, but 155Kai is more than enough. no less than 155Kai though, or you'll run into trouble not killing the boats