Defintiely get a second box of spiders you will need them! I would recommend an electric creation as they can give you some early game scrap to get the spider factory started
For additional models I would recommend Johan as a solid utility piece with a great hammer and he synergises with the rest of the crew, I would also recommend the mechanical rider and metal gamin as both are very good pieces. Also the rail crew, Mei Feng's box, may be a good second choice of master as her box models synergise with Ramos and his stuff works with her, also it will give you two unique masters that can over all the available strats.
Just my 2 cents