Creating a TCG - Checking Mechanics
Note: I Am Not A Lawyer, this is mostly just accumulated internet knowledge, and may be inaccurate.
Card game mechanics are patentable. This means your mechanics could be already be patented by another company.

A patent protects a unique invention or process. It protects it by preventing someone else from duplicating your invention/process for a period of time (typically 20 years).
Yes, Richard Garfield patented tapping. The patent, by my reading, runs out on June 22 of this year (2014). Wizards went back and tacked on some other parts to that same patent, which you can read here. The patent covers just about everything you could imagine in a TCG. It covers building decks, casting spells, the process of trading with others and more.
Wizards is saying that Hex violates a lot of its patents. Hex probably does. Here’s the problem:
Those patent claims are beatable.
For example, they might be too abstract. They might be too broad. Having a patent does not guarantee that it will be valid in the face of someone challenging it. And importantly, if they run out when I think they will, Hex/Crypto can limit the damages they pay out to only the infringing time. After that, Hex isn’t infringing on any sort of patents held by Wizards. They’re probably still infringing on all the patents that early adopters lined up on the internet regarding downloads, backups, dropboxes and other horror stories. Litigating patents takes an incredible amount of money, especially when you’re trying to get it declared invalid one way or another.
Source

While your game is in development/playtesting, this is not a big deal, as you're not charging money, and so the worst you could expect would be to be told to stop.*
Once that changes and you're actually trying to charge for this stuff, you should seek actual professional paid-for advice. Apart from anything else, you should consult a lawyer about starting a company to control the game, so that in the event of lawsuits or contracts, only the assets of the company will be liable.
*: Warning: I may be completely wrong about this.