Like GomesR, I'd suggest you worry less about frequencies and focus more on how sounds work together. That might sound like the same thing, but it's not. try different things, like playing with the gain/volume on each sample. turning each up and down slowly in turn, so you can hear how each sound interacts with the other.
Don't just layer similar sounds together..you'll only end up with more or less the same sounding stuff in the end..try mixing both highs and lows together and playing around with EQ and Reverb on one sample at a time, so you can hear the difference you're making to the overall new sound you're making.
It's all pretty simple really, just jump in and have fun..and make sure to keep notes, so you can repeat the process later if you need to. Some people forget to keep notes when they start out, but it can be really helpful later on.
Oh..and welcome to IDMf.