If you already have Mags and Betsy packs and a bunch of IW uniforms that completely change those characters and make em usable (like IW Buck, IW Rhodes etc) then sure buy BP package. If not, then go for uniforms> Mags>> Betsy>>> BP.
Like god of thunder said. In order of best value you should purchase zero to hero unis first such as winter soldiers IW uni, helas ragnarok etc. Then the deluxe packs (magneto/betsy). Last should be the extreme packs