The easiest way to get points is to play 3 inning exhibition games against a second controller and having them lob you pitches. This will help in getting the hit x in x achievements, plus you get 5 points per strikeout (45 in a game) and 25 points for winning the game. As far as trading cards go, I would wait until you have at least 100/120, preferably 110/120 that way your odds of trading 3 cards in for 1, and then getting 3 of them in your next couple of packs is greatly reduced.