re: Poker & which manager/tracker
I second the motion to avoid the "Get it free" deals unless you know for sure that you'll never want RB or other sign-up bonus on the site that would be far more valuable than a free copy of HM. If it's a site where you can deposit and clear the bonus to get your free license and never play there again, then I guess it's fine, but you never know where you might want to play in the future. Locking yourself out of a more lucrative signup deal would suck. When I first started playing online poker, I locked myself out of a 40% SportsBook (Cake at the time) RB deal to get a free copy of Hold'em Indicator, not knowing at the time what RB was (or that there was better tracking software). Fortunately I didn't play there very much after I cleared the requirements and then they switched to Merge where I already had RB on another skin, so it wasn't a total loss for me.
That said, Merge doesn't offer RB anymore and AFAIK signup deals don't impact your VIP potential, so if they still offer the deal with a Merge skin like Carbon, then it might be okay to do now, unless there are better skin signup deals out there.
And to answer the OP's question: trackers are used in multiple ways. The two primary ways are to gain information on your opponents, and to analyze your own play. At the lowest of the micro-stakes (penny stakes), gathering information on opponents is only marginally useful since the majority of players you're up against are so bad and all over the place that you don't need much information to exploit them. At 10NL or 25NL and up where you run into more grinding regs, then this becomes more useful. However the benefits of self-analysis at the lowest stakes cannot be overstated, and is really the primary value in tracking software.
So yes, no matter the stakes you play, tracking software can be very beneficial if you use it correctly.