i might sound very "potong stim" here.......

Resin kit is much harder to handle than injection kit (Bandai HG, MG r injection plastic kit). In addition, resin usually cause a lot more than injection kit. For now i would recommend u stick to injection kit first, cause to make a resin kit nice, in the most basic level, u need quite some tools n material.....

However, it's still up to u, it's your kit.

Anyway, for your question, i think i used to see resin primer (The first picture) in Time Machine. Go check out there. If not, go back to the shop that sell you the resin; they should carry it. Cause unlike injection kit, resin kit must be painted (unless u like your display kit too look yellow.... without any color). And painting on resin kit must be cleaned thoroughly and almost 100% must have primer to help the paint grab onto the surface.

If the shop not selling primer but just resin kit to his customer....... mebbe u can request them to help you order some primer in.
For the second picture, it's a tamiya gray surfacer/primer. U can get that from tamiya underground. For this surfacer/primer, i recommend u used Gunze/ Mr hobby's; easier to find in town. Many model shops carry it.