In terms of Cinematic/Instrumental music, there are many ways you could go. If you're looking to go the VST route (like I usually do) here's what you could do:
I’m not that familiar with LMMS, but if it supports VST plugins you could just skip to the next paragraph. If it doesn’t, get a nice digital audio workstation (DAW). Some good options out there are ProTools, Cubase, Reason, etc... Just make sure it supports VST Plugins.
At that point, there are a few different orchestral VST instruments out there. As the old saying goes, you get what you pay for though. Here are just a few options: MOTU symphonic instrument, Garritan personal orchestra, and East West symphonic orchestra. I used the MOTU instrument on a previous album and thought it was great for the price. If I had to do it over again though, I most likely would have used the east west series...although it's a bit more expensive.
I'm sure other, more seasoned musicians on this forum might recommend other options too, so maybe one of them can chime in.
I hope this helps.