My husband says that if you can’t afford the Mossad HaRav Kook for the Rashbas and Ritvas, either hold off altogether, or buy the cheapest set you can find in the meantime. The Rav Kook set is really, truly worth it and no other set is comparable. The footnotes and annotations of the Mossad HaRav Kook Rashbas and Ritvas are written by serious talmidei chachamim and add, k’vyachol, nearly as much to one’s understanding of the Gemara as the Rishonim themselves do. Look in particular at the Ritva on Yevamos, which is two very thick volumes in which the commentary greatly exceeds the text of the Ritva.
As for the shita mekubetzes, I’m not familiar with the different sets so unfortunately I can’t make a recommendation. But I’m curious: why do you want one? It’s not difficult to obtain the basic Rishonim al haShas (Ramban, Rashba, Ritva, Ran, etc) and the Rishonim quoted in the shita mekubetzes are much less likely to be brought down l’maaseh.