I've been taking marks that are representative of the decks/element that won said mark code for me. (i.e. most wins that day) The first tourney I won, I used miracle in every deck, and nobody else used miracle, so I took mark of light, for example. My air mark I won with an elite firefly/UG deck, my earth mark with a pharaoh/earthquake deck, and my time mark with a dunescorp/oty/momentum deck. For leagues it was a tougher choice, since many decks were involved, but I took entropy for dbh/speedbows and fire for firestall. I've also been going with the rule that if two elements are equally viable, I take the one first that I don't have (so I took earth from the pharaoh/EQ deck, since I had a time mark already)) and if that doesn't decide it, then simply the element I think a mark will be more useful for. (when I took the time mark in the first place, for the time/gravity deck)
For upgrades, I'd do it once I got six, but until then, I'm not going to up them. I also wouldn't take a nymph if I could get a mark, simply because nymphs can be gotten from the oracle, and only codes can currently get a mark, even though nymphs are actually better in most cases.
For taking marks, I see two ways to do it. One is to spread them out, which is largely how I've been doing it, as I have six different ones,, and the other way is to focus on one element you really like and always get that one, or at least 6, and then go on to another. I don't have any particular element I'm a fanatic over, so I figured the above way of taking a mark for the deck that wins it made sense to me. It should also mean that I will win more marks for elements that are more successful, and elements that win less tourneys I will have less marks for, so that in theory I will use the marks I select most often.
