Like anything else, a rookie first rounder is worth whatever someone is willing to pay for it. That "worth" will fluctuate through the year. At this time of the year, rookie firsts are near the cheapest they're going to be all year (the cheapest is typically around week 5 or 6, when no one has been eliminated yet, everyone is thinking about loading up to make a run, and no college players are really standing out from the pack yet). At this point of the year, it's typically difficult to trade a first rounder for someone who is putting up reliable points, because other teams can't envision weakening their immediate lineup, even if there's a long-term payoff. The corollary is that, at this time of the year, it's usually possible to trade a player- any player- who is putting up consistent points in exchange for future firsts, if you're willing to take the short-term hit to your lineup. New dynasties are always difficult to get a handle on though, especially if you're playing with other inexperienced owners, simply because NO ONE really knows how to value those firsts yet, and everyone is being cautious because they've never done it before.
As for my philosophy towards future firsts... in my mind, building a dynasty roster is all about acquiring cornerstone players. Cornerstone players are players who are (a) young, (b) proven, and © special talents. That's a very powerful combination of attributes. Player value in dynasty is extremely volatile, and guys who today seem like really solid pieces will tomorrow be completely worthless. The only guys who will hold their value over a 3-year window are those cornerstone guys, so if you can trade some non-cornerstone players for some cornerstone players, those trades will always look like steals in hindsight. To give an example from my leagues... back in 2010 I gave up Mike Wallace, Knowshon Moreno, and Joe Flacco for Brandon Marshall, a 2nd, and a 3rd. At the time, it looked like a ridiculous overpay, but what has happened since then? Wallace's value has tanked, Moreno's value has tanked, Flacco's value has stagnated, and Marshall is still a top-10 receiver three years later. Approach the Brandon Marshall owner with that trade today and he'll laugh at you. Typically, the guy who wins the trade is the guy whose side retains his value the longest.
With that in mind, at this time of year, I'm usually looking into packaging together some guys who I don't really believe in to try to get future firsts. Usually deals like that are available. In the past, I've managed to trade James Jones for a future first and I've managed to trade Lee Evans, Ben Tate, and Stevie Johnson for two firsts. When a team with superbowl aspirations suffered a late injury at RB and was forced to start garbage at his RB2 position, I traded LaDainian Tomlinson (when he was with the Jets), Brandon Jackson, and BenJarvus Green-Ellis (when he was still with the Pats) for Stevie Johnson and a future first. All of those trades were fair value at the time (the Stevie / 1st trade was a little bit more than fair value because the guy was desperate, but it didn't raise any eyebrows in my league). Those were all just guys who I thought were mediocre talents and unlikely to ever become cornerstones, so I moved them for some lottery tickets. I didn't luck into any high picks out of those deals- those picks wound up netting me 1.07, 1.07, 1.08, and 1.09 in various years' drafts- but I still turned those late picks into Greg Little, Randall Cobb, David Wilson, and Le'Veon Bell. Cobb is a cornerstone talent, and Wilson and Bell might yet prove to be as well (although I've already cashed in on Wilson and traded him away for Brandon Marshall).
Also, people believe that first rounders are risky assets because they might bust, but established players might bust, too (witness Mike Wallace). Draft picks never get injured, they never have a bad game, they never get suspended. If you get three or more draft picks, even if all three are late, you're usually going to walk out of the draft with at least one future stud. Their value always increases as time goes by, and they don't take up a roster spot, which means you never have to make tough decisions about who to cut. And on occasion, even a "bad" pick will hit the jackpot and become top 3 because even good teams will sometimes get screwed by injuries or schedule luck. All-in-all, first round picks are about the safest investment you can make in dynasty leagues.
