Very doable solo. Just remember this isn't a mindless run in blindly hack n slash, that sort if behavior will get you killed, frequently. Planning, prep and caution are important.
Also you don't have to fully upgrade gear level. If you're good at combat you can use the first level of gear for each biome just fine and save a lot of time farming mats. However if you are struggling you can invest time in upgrading your gear levels to make things a lot easier. The choice is yours.