I need to make some texture with circle in circle and I did it manually, but I would love to know how to make that process a little bit faster. I'm sure illustrator has feature for this but I didn't find.
You can do that with the Blend Tool (w). Create the largest and smallest circles. Select both circles. Double click the blend tool, select specified steps, select the number of intermediate circles you want by indicating the "specified steps". click on one of the anchor points on one of the circles, then click on the same/corresponding anchor on the other circle (i.e., click the top anchor on both).
If that doesn't make sense, look up using the blend tool on YouTube for clarification.