The best is Yupo Paper. However, it is rather pricey if you want to do a lot of projects with alcohol inks. I found that using the back of Hp photo glossy cards (4 x 6 inches) was the next best surface. It has a grittier surface and works well. Here are some samples. Notice I have doodled in the samples with black micro perm pens.
The top two are on Hp paper and the bottom one is on Yupo.