The fastest and often the cheapest method is to look for travel agencies in your city that offer Russian visa. Often Russian travel agencies offer this service.
The advantages of applying for a visa through a travel agency are significant. It is faster, cheaper and easier compared to online services.
Applying for a visa through the Russian consulate is the least expensive method and usually the fastest. Unfortunately, however, it can also be the most challenging method.
There are significant disadvantages if there is no Russian consulate near you. Often this means that you have to travel long distances by car. In addition, I have found that it is difficult to reach the Russian consulate by phone.
Online service: The easy solution to apply for a visa from the comfort of your home.
The disadvantages are quite big: online services are expensive, usually take a long time and are complicated. In addition, you have to send your documents by mail.
Our personal recommendation is the travel agency, even if the direct way via the Russian consulate is the cheaper way. However, our experience with them was quite bad.