Reverb, definitely. The Calf Reverb is one of the most powerful reverbs shipped with LMMS, try it.
As a general rule, equalization can be used for mild tweaking or powerful modification, but you want to avoid it and try to modify the base sound as much as possible. This way you don't get a sound that's too obviously equalized and/or muffled. At least, that's what I feel. You can use it for highpass/lowpass, but if you're making a huge change, silencing out a lot of the sound and leaving only a bit through, then maybe your base sound is just too different from what you want, to work with peacefully.
Try the LMMS echo effect (Multitap Echo), with a tempo-synced length, on the "cooler" less warm-feeling instruments. This adds a nice sparkle.
The TAP Stereo Echo adds a nice spatial effect. But if you want a simpler spatial effect with lesser echoey effects, try the "Stereo Matrix" effect. Be warned, this can cause a phase difference, you want to listen to your sound in Mono too and make sure it sounds balanced.