Is it conventional to talk to spirit guides through the cards? Or even possible or recommended? I think I did so tonight and I probably should have researched better beforehand. I did some chakra clearing and meditated and focused on gratitude and love beforehand so that I would be protected, but I met two spirits and one may not have been good.
Am I worrying for no reason? Any advice?
No, you are not worrying for no reason. If this is something you really want to do, preparation is key, just as it would be if you were planning a hike into unknown wilderness.
I have worked in this realm for quite a while now, and in my experience, any time you invite interaction with the spirit realm, simply clearing one's chakras, meditating, and focusing on gratitude and love will not shield you from tricksters and non-human entities. These low vibrational energies can and will take on the personalities of a loving guide, or your departed loved ones, in order to have a little fun with you. You need to have a way of knowing absolutely that you are communicating with the spirit you wished to connect with, not some low life who thinks it's funny to mess with you. They will often start out very loving and give you a lot of information that sounds like it is coming from your spirit guide or a loved one. Then when your guard is totally down and you trust them because you think you know who you are dealing with, they will say something devastatingly mean or frightening.
If you are serious about wanting to work with spirits, you will need to do some serious work beforehand, or you may end up with a lot of dicey energy around you that I guarantee will be more difficult to eradicate than it was to acquire. Opening yourself up to any and all spirits who want to come visit you is very much like unlocking all the doors to your home and then going into a bad neighborhood and posting a sign that reads "Open House - Everybody Welcome!" with your address underneath.
I highly recommend studying some material on working with your own guides, such as Rose Vanden Eynden's
So You Want to be a Medium, and establishing a solid connection with your Gatekeeper guide and an archangel or two before you venture too much farther into this area.