First of all kudos for smartly using Modafinil. You've done your research and that's great to hear.
Personally I've never directly used it for depression. My goal is same as yours, being productive. Now here comes the interesting part.
Modafinil has three major effects on me. Sleeplessness, motivation, and focus. Motivation and focus kind of seem a little mixed. As in I feel like "There's my phone, I can open up facebook. My friends are having a good time, I can enjoy them. But I will not, I'm a responsible man".
It helps me in pushing me to improve myself. That's probably the opposite of depression. So it doesn't reduce depression like anti depressants do. Rather it boosts your will power. Again, will power can also be placed on the opposite of depression.
I personally think that modafinil works when you want it to work. It works when you can't focus but you really want to.
Talking of other things which boost modafinils potency. I choose tea over coffee. Tea has both caffeine and L theanine. L theanine gives you the calmness, coffee gives you the stimulation. Tea basically covers all the other vacant areas which modafinil leaves and coffee misses.
Personally I've never felt that exercising has increased the potency, though I'm an incredibly fit person otherwise. Modafinil doesn't kick extra on the days I don't work out.
Meditating has enormous effects. I open my eyes as an entirely different person feeling like twice the IQ when I do this. Wake up, wash my face. Drink tea with a 200mg pill. Sit down and meditate for ten minutes. When I open my eyes after doing that, it's just a completely different person opening his eyes.
And of course water, I routinely make sure I'm drinking one litre per hour. That's an enormous quantity, but without that I the back of my neck starts to feel a little dry and cramped and strained.
I also shower six hours after ingesting Moda. It's a nice break and gets the blood flowing again. Plus the stuffiness and the dampness modafinil induces goes away. It's like taking a 200mg pill again.