I personally only use drum samples for building together my own drums. I prefere to do all the melody stuff myself when it comes to Liquid, but that's up to you. Drum samples can be found in pretty much every sample pack
Also check out http://www.soundstosample.com/
+1, I use scarbee vintage keys for kontakt and there's libraries like session strings to cover your bases for acoustic strings. another option would be omnisphere, it has all types of strings and a couple great rhodes patches too. if you have ableton, maxforlive has great libraries which definitely rival kontakt. I find the maxforlive libraries better if you want that old, sampled sound. I like the maxforlive libraries better for that reason, whereas the "session *****" kontakt libraries sound like they have more clarity but a bit too orchestral for liquid dnb. i prefer the grittier string sound from maxforlive to give that sampled vibe. you also have lounge lizard which is amazing for rhodes, electronic pianos, etc.