My (nooby) advice:
First card as Spain is always 3 villagers. Unlock that card asap. You put all vills on food, and age as soon as you can with as little idle TC time as possible.
Secondly, for market upgrades, I would generally get them from the transition from age 1 to age 2 (Discovery ->
Colonial) with most civs... as Spain I don't exactly do that personally, but you're pretty new so you could try. Just know that they make a good difference when you do get them.
As for second cards... my advice here is to read the number of strategy and build orders that have been posted here at HG. They're great if you want to get into the game. They helped me a lot when I started:
http://aoe3.heavengames.com/cgi-bin/forums/display.cgi?action=ct&f=1,36513,,10
I can say now though, 300 food, 2 vills and conquistador cards aren't very useful ones. When you make your deck, you should have a fair balance of resource cards, military unit cards, economic upgrades, and military upgrades. A useful thing to do is look at other player's decks online. HC tab > Search for user. Definitely read those guides I posted.
As for graphics, my personal opinion is that it's best to have the maximum performance possible, it just feels better when you play. Literally. I have mine down to the bare minimum (except for one option). Experiment yourself and see how it works for you.
As for TAD or Vanilla... again this is my personal opinion, but if you want to get good, don't play Vanilla, the competition is harder on TAD, so you'll get better. Also, TAD and TWC have more civs and diverse features you can use that make the game more interesting to play imo. Another tip, I don't recommend playing Treaty. Idk... a game or two to see for yourself is what I advise, but "colonial rush games" are harder and more satisfying to win.
Something else that could help a lot to grasp the game are recordings. You may or may not be aware of this feature and even if you didn't ask about it, I'll mention it. ^^
Recs are games that can be replayed with you as God. You can see everything that's happening, from the perspective of both players, with or without Fog of War. Recs are very useful for learning strats, finding mistakes, and showing off playing skills.
Whenever you rec a game (the "Rec" button is at the bottom right had side of the screen) the file is made in your "Savegame" folder.
Location: My Documents/My Games/Age of Empires 3/Savegame
Remember, look in My Documents, not Program Files. The "Savegame" folder is where you put recs that have been downloaded. Also keep in mind that you can rename your recs, as "Recorded Game 1", "Recorded Game 2" can get confusing. Try to name them with players, civs and map in the title.
Now each rec is different. There are three different types of recs:
-Vanilla Recs (no expansions)
-TWC Recs
-TAD Recs
They each have a different ending:
-Vanilla>> .age3rec
-TWC>> .age3Xrec
-TAD>> .age3Yrec
To view TAD recs, you need TAD, to view TWC recs you need TWC...
Where to find good recs? www.agesanctuary.com! Make an account there, and you can download recordings from pros. These are excellent for learning, I recommend it.
hope it helped.