Originally Posted by Cogwheel
As for how to get your cards? The five rectangles by your spirit bar are your card gauge. When you deal damage, take damage or fire projectiles/use special moves, your gauge charges up. When a rectangle fills up, you draw a card. Your hand holds a maximum of 5, and your deck has 20 cards in it. Simple enough. Some characters do better at charging the gauge quickly, and the system means that going pure melee is going to end with you having far less cards than your opponent.
Oh, and by the way, no, I can't give good decklists here. You can consult me for help, but in the end, different things work for different people. That said, I can tell you that Magic Potions have no business existing. At the very least, replace them with Grimoires.
Just some notes I want to add, taken from the Wiki...
There are three main ways of filling the card slots: connecting hits, spending spirit, and having the opponent connect hits on you. In Hisoutensoku, each slot in your hand requires 500 card points to draw, unlike in SWR. There is no difference in how long the cards take to draw.
Connecting hits (blocked or unblocked) fills the gauges rather fast, with an amount that seems proportional to the attack's base damage. Firing B bullets gives you 30 points, firing charged B bullets gives you 50 points, firing any C bullets, charged or not, gives you 50 points. Doing a special gives 50 points, however there are some exceptions to this. Spells do not give points towards drawing cards. Taking damage also gives you points towards your next card, at the rate of 1 point every 20 health lost, meaning you gain a card from damage upon taking 10k damage. Chip damage and gradual damage, such as from Yuyuko's or Reisen's poison spells, do not give any card points, however.
Also, the Magic Potion card has its uses. The Magic Potion system card will greatly increase your spirit regeneration for a duration, and instantly recover crushed orbs. You know when you hear a "clank" sort of noise if you block incorrectly and see one of your spirit orbs turn orange? That means it's been crushed, which renders it unusable until it's restored. This would only otherwise be possible by waiting, so if you've had several orbs crushed by wrongblocking or Border Escaping, Magic Potions can be very useful. Or if you just like spamming bullets.