Every night before I would go to bed I'd send off all my recyclers and fill-up all my fleet spots. I would recycle as far as the next gax on either side of my own. This was a great way to get resources beyond what my mines would produce, and rise quickly.
I would go for the biggest debris fields, flipping system by system until I filled all my fleet slots. I would generally avoid anything below 7000k, unless I could not find anything else. I would also look at how much deu it took for the trip, but in general it is always profitable with a larger debris field.
Note, a lot of times if you are recycling a gax over you will be completing with local planets which can get there quicker. If this happens the debris fields maybe gone before you arrive. Therefore, do not commit all your recyclers to big debris field far away, because they may come home empty, which would be a loss of resources.
Instead, send a few to big fields and some to smaller fields. This way you can wake up and find resources. Note, many of these trips take several hours, so don't do it unless your going to be away, or don't fill-up all your fleet slots.
I'm attacking planets now, but this really helped me grow fast, and I had 18+ recyclers in each of the two gaxs I have planets in.
In general, also, don't try to grow to fast in rank by building things you don't need. Focus on research and enough defense to be ahead of your rank in these areas. I went for plasma turrets before battle cruisers, research lab before nanite factory, Combat research levels over building numbers of weapons. Ships sitting on a planet collecting dust are resources tied-up (same with defenses, to a degree), wasted.
Play with the battle simulator and see how many ships it takes to take out simple defenses, and then decide how long your going to be growing a fleet to take on a planet. I say, mine and recycle until you can build better ships in mass and have the weapons research superiority. Grow in rank fast without gaining a superior advantage in research and you will find yourself very behind.
Have fun! Recycling also allows you to scout and figure-out your gax (and neighboring ones) and who is doing what where, and a strategy for moving forward.