I wouldn't rule out Tolstoy (for example, 'Anna Karenina' is considered by Nabokov as one the greaters novels). His style and prose are often not so convoluted, he seems to like simplicity sometimes, I would say he is the easiest to read of all Russian 'giants'.

Bulgakov is a good choice too (as a 20th century author).

Lermontov, Pushkin, Saltikov-Tschedrin, Goncharov, Turgenev, Gogol, Dostoevsky are giants. But it seems they would be difficult to read due to vocabulary (sometimes outdated), literary devices. It is good to read them while keeping in mind that there are hundreds of outdated words (requires time to check the meanings).

Modern writing in Russia is moslty represented by entertainment type fiction or documentary prose. (maybe Веллер could be an option).