This is a general description of the store in Omsk.
There are at least 2 malls that i know of in Omsk. They are a reasonable size and have a good variety of American and European goods. There are no shortages of items and all of the food items were very fresh. Russian food does not contain additives, it is organic. This is a carryover from the Soviet era when farmers could not afford fertilizers, etc.
The food there is fresher than it is in the U.S. I did not become ill and all of the food agreed with me quite well. All of it was very good and the store and restaurants I went to in Omsk were VERY clean.
What to buy: I don't drink much but I can tell you the vodka is LETHAL - it burns going down. So, if you're into that, it is a good buy.
There are some things unique to Russia (such as Mastroika - nesting eggs/dolls), authentic vodka, soviet era items and crafts from Omsk.
What to pay: Many of these items can be purchased from $2 and up
If you go in the street just in front of the train station (on the other side of the square), on your left you'll find a big bazar...you can buy almost everything here, most of all dresses.
prices are often good, and it's funny to deal with the sellers.
This is an interesting place to visit in winter: if you aren't properly dressed for siberian winter, you can buy here something warm to wear.