1st, once you pick your colors for the gradient take the time to mix blend the section where they touch with a toothpick. This will automatically create a beautifully blended gradient when the sponge picks it up with out you having to do a lot of work with the sponge.
2ndly, wait for your polish to be absolutely dry in between each coat with the sponge. I was never patient enough for this before and often ended up pulling off bits of color with the sponge.
Hope those tips help improve your sponge gradients too! Here is a pic of the polishes I used.
First I painted my nails white using Scorch by Illamaqua with 2 coats so it wasn't streaky. I used a coat of OTD quick dry top coat.
As you can see from the polish bottle picture, I only used 2 colors to create each of my gradients. For the purple gradient, I used Sinful Colors polish in Sweet Tooth & Amethyst. The Gray and Yellow was Zoya in Pippa & Kristen.
You can see how well just taking a few seconds to pre mix the polish creates that beautiful gradient. This was two coats of sponging, making sure it was all the way dry before I applied the second.
Lastly I tried to use my Winstonia plates that had an awesome looking tree on plate W102 to stamp on my nails.
I say try because for the life of me I could not get it to stamp properly so in the long run I ended up hand painting with some black nail art polish so that is why they all look a bit different.
Overall, I was pretty happy with how they turned out. Hope you like them :)