if i would be you, i would better stick with the plugins which are packed in ableton as i think they are pretty useful, and for saved money, i would upgrade monitors or invest in accoustic treatments.
as for your list:
Drums
NI Battery,it is great for what it is, but its well overpriced, Linnplug RMIV the same,. stick to ableton impuls/drum racks, and buy Sonic Charge Microtonic.
Synths
Hydra - yes, Sylenth 1- yes, NI FM8- yes, also look at Rob Papens plugins, Albino 3 and Predator are top plugins,,. also scheck NI Absytnth for pads and atmos,... dont waste money on Lo9ungeLizard, Cronox, Slayer or Minimoog...
Effects:
i would suggest you to better stick with free plugins until you realize what plugin you cant use as a free version and then buy it. deffinitelly check Bootsy collection, TAL collection,....and many more, go thru Free VST thread and you find lot of useful stuff...
as for mastering, dont waste money on the plugins, better find soemone who got skills and send tracks to them to master for you, it will cost you less money and i bet result will be much better.