This is what I have, I bought them in 2015 https://www.amazon.com/gp/product/B000Y4HI7A/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

To answer your card questions:

it says draw a card then has 0 attack associated with it unless you've previously played a certain type of card. Can I play that card by itself to draw a card? Or do I have to use it as +0 as part of an attack to get that perk of drawing a card?

Unless the card specifically says that you must do something in order to play it, you can always play the card. When you do, you get the Attack and Recruit printed on the card immediately. Then you resolve the card text in the order it's printed, ignoring text that you don't meet the requirements for.

So with Wolverine's Animal Instincts card, you play it and immediately get 0 Attack. It's important to note that the card does have Attack, it's just 0 at this point. Then you draw a card, because that text does not require anything. Then, if you have previously played an Instinct card, you get +2 Attack.

in the case of Nighcrawler, one of his cards has two requirements on it to get the bonus. Do you have to have played both of those card types previously in the turn to get the bonus, or just one or the other?

You must have played both. Some cards also have a requirement of two of the same type, and that applies the same way- you need to have played two cards of that color in order to activate that part of the card. Captain Marvel has a card that requires two Green and two Blue. Some cards actually have multiple colors on them, so that's something to pay attention to. Playing a card with more than one color counts as playing one of each. Essentially, you just count the symbols in the top left of all the cards you've played.

It's also worth noting that Sidekicks count as cards that have been played this turn, both in card count and in color. Just a thing to keep in mind for when you get the expansion with Sidekicks... I don't remember which one that was.

As for card sleeves, I just use Ultra Pro penny sleeves. Here's the ones I ordered. They are sold in packs of 100. You can either pay $5.98 for single packs, or you can use the lot set that I linked which lets you choose between 10, 20, or 30 packs of 100. I got the 30 pack, I still have a couple hundred sleeves left over, but it's the best bargain and you can never have too many card sleeves in my opinion.

I went with this one, it's a bit pricier than I'd like, but it's pretty nice. Used a little duct tape to make sure everything stayed in place once it was set up as I wanted.

I chose that one because it works well with these deck sleeve which I got an obscene amount of.

That makes sense. I've always assumed penny sleeves were about $1 for 100 sleeves, though I'm sure inflation will kick in ay some point.

I just searched on Amazon and here's one I found (with free shipping, too!) https://www.amazon.com/dp/B000Y4HI7A/ref=cm_sw_r_cp_apa_XgwTBb8AZ6W92

I used these generic ones off amazon: https://smile.amazon.com/dp/B000Y4HI7A/ref=cm_sw_r_cp_awdb_t1_nQR3Eb7FPP1B9

But I recently came across these and have been wanting to try them out: https://smile.amazon.com/dp/B07QC2FTBV/ref=cm_sw_r_cp_awdb_t1_RRR3Eb83HMVCX

I second penny sleeves. I use these---$8.25/1000.

Pros:

• the thin, slick nature makes them shuffle really nicely, IMHO
• unlike heavier sleeves, they actually cost less to use than it would to just replace the entire set of cards with new ones
• they are actually less than a penny per sleeve (edit: sorry, that's my price with Amazon Prime (free shipping), but you'll come out around $.01/ea regardless)

Cons:

• as /u/Torvax said, they are slippery. I'm perfectly used to it and only occasionally do I drop some (when I'm handling a really large stack and I'm not careful about it)

Also as /u/Torvax said, Pathfinder ACG does have "many piles" :). But none are that large during actual play, and I have no problem with keeping cards stacked or anything.

tl;dr: penny sleeves are the only option that makes economic sense for Pathfinder ACG. I recommend either them, or no sleeves at all.

edit 2: sigh, I didn't answer either of your questions. The first one I don't know, the second...you'll need about 500 for the core set, and each adventure deck thereafter (of which there are five) adds 110 cards. I believe the Character add-on deck is also 110.

edit 3: AAAAGGGHHHH A THIRD EDIT! I forgot...another nice thing about the cheap sleeves: the player cards are actually designed to be written on (WHAAAT?) when you "level up" skills etc (tick boxes to check off). With the penny sleeve you can just Sharpie on that damned sleeve and a) not ruin your card and b) just grab another sleeve if you make a mistake or change you mind or something.

What size are you looking for? I had a few extra sleeves I bought from a few years back. And then recently decided I wanted to sleeve SmashUp and had to buy 1000 more sleeves to do so. And I found the old ultra pro in the size that I wanted on amazon after 20 minutes of looking. I just used 2 5/8” x 3 5/8” of the ultra clear because they’re cheap and you can buy them in bulk. If they’re not the size you bought before they could be bought to resleeve everything for a great price.

You get 10 packs of 100 for about $10 plus shipping. Be careful when using this though because these are supposed to be ultra pro 2 5/8” x 3 5/8” but some sellers have been sending other brands and the offer has been updated to allow it. You can use the questions to make sure you use a seller that gives the ultra pro ones compared to another brand and you can always return them after buying and buy again from a different seller in the event you don’t get ultra pro.