It isn't very mean to ask for a few spare cards from people. Just be sure to not ask someone you barely know.

Don't expect cards, be kind and courteous no matter what!

When there are games that have a four pack for about a 1 or two, be sure to capitalize on this to get more cards.

Most people don't care about their steam level, and there would be at least one person willing to give you 5-10 cards for one copy, and then repeat this process over and you could have up to 25-50 cards on average!

There is a website that lists the lowest costs of badges, from the lowest costing badge to the highest. This is essential to geting levels quick!

http://steam.tools/cards/#

I'm sure most of you already have it, but the Community badge is a must for starting out!

The badge has many levels of completion:
Level 1: 100xp
Level 2: 200xp
Level 3: 500 xp.

When completing about 26 objectives, it gives you the last level, which is 500xp. This will (assuming you are level 1) bump you up by 5 levels.

The objectives are extremely easy, so this is free XP basically.