... what I heard in Demos...
Don't judge products based on the company demos. My wallet learnt that the hard way.
Better to listen to actual users and reviewers on YouTube for example. Daniel James is my favourite, closely followed by
@Cory Pelizzari. You should definitely watch the whole of Daniel's review of AR1.
Your approach of having a starter all in one library supplemented by free bits and pieces is perfectly viable. Albion One, Nucleus, Inspire or one of the Project Sams would be fine as the core library. Please forgive a self example as an illustration. Hopefully it sounds alright and offers an alternative approach to buying expensive specialist products.
Paid-for stuff
Nucleus
Majestic Horn
A couple of synths, NISS and various percussion from Komplete/Kontakt
Free stuff
Angry brass and some strings from Performance Samples (no longer available I think)
Some string patches from Spitfire LABS
A bass guitar from Pianobook
Leeds Town Hall organ (Samplephonics)
Mihai Sorohan Vowel Choir
Thunder Taiko (Strezov Sampling)
Bits and pieces from the Project Sam free orchestra
Some traditional Korean string and percussion instruments (can't remember from where, sorry)
Epic Trailer Sounds (Audio Imperia)
Free Angels (8Dio)
Cling Film Frame Drum (Kralc)
Wooden Percussion (Kralc)
Raw Power Metallic Percussion (Riverwood Air)
Cinematic Synthetic Drums (Impact Soundworks)
I made some of the trailer FX myself and found others in various free packs.