Tips of becoming skilled Engineer

Hi guys , i am a developer and working on Ruby on Rails for the last 3 years. Working on web applications or such a long time gave me a good experience but i dont know where i will end up. I want to work for some challenging companies or may be startups because i think startups allows you to experiment things out of the box but i dont know what should i do to boost my skills that meet the needs of any company. I mean what skills should i focus on to become an asset. In the meantime i am also interested in data sciences and wants to play with big data as a data analyst but i dont know in which direction i should take steps. Your suggestions and advices are welcome.