I'm a novice too, but I've bought & dilluted some things. I suggest keeping most of every concentrate you buy in its original container and experimenting with different dillutions. My experience is that most things smell different at different concentrations - 100%, 10%, 1%. Starting with essential oils I find that even 0.1% is easy to smell. I suspect most commercial perfumes have some components at 0.1% to just tweak the scent of the major components.
The usual recommendation is to dilute with Everclear or the highest proof vodka you can find. I think the more alcohol the faster the evaporation. That's probably why a lot of internet recipes call for diluting with a mix of alcohol and deionized water.
Get a notebook, write down everything you do, put labels on every bottle you mix, and have fun. I don't think you'll get anything that smells like fish.