[6] In July 2017, Gailums set a new personal best with a throw of 81.91 meters at a competition in Valmiera, which also became a new world junior best for the year.

[10] The following month, he finished 14th overall in the qualifiers at the European Championships in Berlin with a throw of 78.10 meters, which was not enough for a place in the final.

[11] In July 2019, Gailums finished in fourth place at the European U23 Championships in Gävle with a throw of 79.81 meters.

[17] The following month, Gailums won silver at the Latvian championships in Valmiera, only beaten by Rolands Štrobinders.

[19] The following month, Gailums competed at the European Championships in Munich, where he finished in sixth place in the javelin throw.