Lemongrass goes with almost anything, certainly anything that lemon does. It also works with most florals.
To get initial ideas, I pair the cap with other FOs/EOs, even ones I think won't work, and run them under my nose. If the caps smell terrible together, just recap the bottles... no harm done, no oils wasted, no droppers to clean. Just be sure to note what works or didn't work.
Trying two caps just now, I ~really~ liked LG 1 to 1 with oakmoss FO, with cedar EO (Atlas!), and with musk FO, even with pepper EO. But not 1:1 with amber or vetiver, though they might work at greatly reduced amounts as touches.
I would then add drops to vials or jars, putting 1:1 drops in one vial, 2:1 in another and then 3:1, to see which one I like better. Sometimes I add a contrasting cap to see if it softens or deepens the blend, usually at a lesser rate. Finally, I pass my favorite sample blends under as many noses as I can find and ask what they think... usually there'll be one or two clear favorites.
What works for me anyway!
http://www.pinterest.com/pin/create/extension/