As part of the normal backlink profile you would absolutely expect to see some nofollow links (In many cases, you can expect to see more nofollow than follow (Moz's inbound links have a ratio of something close to 40% follow to 60% nofollow). Of course, if you only have a few inbound links there's every chance that 100% of them could be passing equity. However, as your site grows, you'd definitely expect to see that percentage drop off. Being honest, I can only see this ratio being something to concern yourself with if you are trying to make your backlink profile "look natural", rather than allowing to develop naturally. Often, the kind of places that allow you to "get" dofollow links (i.e. paid links/directories etc.) are of lower quality and Google will have a pretty good understanding what they're up to and simply discount the links, which could see you investing a lot of effort and gaining nothing of any worth at the end.
So, in summary, there is no optimal ratio of follow/nofollow links, only good links (natural/relevant) and bad links (paid/spammy). Concentrate your efforts on building great contents, satisfying your visitors (by giving them what they want) and building relationships within your vertical and you'll gain far more from fewer links. It may seem counter-intuitive, especially if you see your competitors gaming the system, but their success will likely be short-lived.
I know that the "build great content" and "putting the user first" messages can seem a little trite, but you hear it a lot because it's true.
Good luck with your project!
