I hear good things about Seachem Flourite and I was thinking about
purchasing Flourite and using
sand instead of gravel to use on top of the flourite.

Others have advised you not to mix for a 10 gallon tank. Attempting to layer is
even less desirable: the sand grains will fall through th Flourite pretty
quickly. You will not get the result you were after. Straight Flourite is
awesome in all ways but cost. For a small tank, you only need one bag, so you
can't save any money anyway.