As far as we understood, you are interested in Kyiv-Maribor-Kyiv. If so there are two basic cheap ways to travel here:
1) Get Ukrainian domestic train from Kyiv to Chop ("platkartnyi" starts from 90 UAH), then purchase Chop-Budapest-Chop ticket in Chop (app. 40 euro).
There is only one direct train from Budapest to Slovenia avoiding Croatia - it departs Budapest Deli at 12:03. So this is the time you need to be in Budapest (to do so you will need to use sitting carriage of train #15 Moscow-Budapest - it starts from Chop at 6:30 and arrives to Budapest Keleti at 11:17 - 45 minutes is enough in order to get from Kelelti to Deli and buy your ticket). Budapest-Maribor-Budapest ticket purchased in Budapest will cost app. 35 euro. But this 12:03 train goes from Budapest to Ljubljana not via Maribor exactly, but transiting Pragersko - only 20 minutes train ride to Maribor from there, trains Pragersko-Maribor go rather often (here you can find all the timetables -
http://www.slo-zeleznice.si/en/passengers).
2) Other choice is to "hunt" for WizzAir Kyiv/Katowice-Venice(Treviso) flights, but unfortunately for you they both leave only on 28.11. From Treviso it costs only 8 euro to get to Slovenian town of Nova Gorica. If you are interested we can elaborate more on how to commute from Treviso via Nova Gorica to Maribor.
Feel free to ask questions
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