You can login to DTube, Steemit, and Busy all with the same username and password, so there is no need to create another account. The difference between busy and steemit is simply the design of the layout and certain features, but the content is the same on both. For example, busy has a more detailed notification feature and allows you to play videos in ur feed instead of opening up the article.

I cant give finanvial advise. However, I do think Steem is at a good price right now. If you just buy STEEM you only benefit if the price increases, but you can withdraw STEEM at anypoint. If you convert your STEEM to STEEM POWER you can benefit from both a potential price increase and it makes your vote worth more. The only downside is that you cant withdrawal all of your STEEM POWER at once; when you want to withdrawal your steem power you can only withdrawal a certain percentage every 7 days. Basically if you plan to be actively using the social media aspect longterm you will make more money by having STEEM POWER compared to STEEM.