Xeoni wrote:
So once I can afford to summon a creature with tapped land cards, I don't need to pay mana for that creature to cast spells anymore? I feel like I'm over complicating this. Oh and wtf is a plainswalker
Let's take a look at a couple of cards.

Alright, so once you pay the 1 white mana (W), you can freely attack and block with this creature as long as it exists on the field and nothing is preventing it from doing so.
This creature has an activated ability though. At the cost of a white mana and tapping the creature (it must be untapped which means you can't attack with it the same turn you activate it's ability) you can tap any target creature, even one that's already tapped.
Now look at this one.

Once you pay the 1 colorless and 1 white mana (1W), you can freely attack and block with this creature as long as it exists on the battlefield and nothing is preventing it from doing so.
This creature also has an activated ability! This one however doesn't cost any mana to use. You simply tap this creature and then you can tap any creature with a power of less than 3.
So in short, unless a creature's abilities say otherwise or have a cost that includes mana in them, you do not have to pay anything passed the initial cost of the creature to use them.
Fun Tip: Now, you can't attack and tap a creature with one of the above, you can however, block a creature and before damage, tap and tap an untapped creature (say a potential blocker for your oppoent).
It has it's uses.
-----------------------------
Now, on to Planeswalkers. They're a bit more complicated but shouldn't be too hard to understand.
You summon them like you would creatures but they don't function like creatures. They can't attack and they can't block. Your opponent however, when he declares combat, can choose to attack you or your planeswalker(s) so that you can block accordingly. Your opponent can also target him with direct damage spells and such.
A Planeswalkers "Loyalty Counters" or Health, start at the number in the bottom right corner.

So this planeswalker starts with 4 Loyalty Counters. The number of counters goes up or down as designated by the cost of his abilities. If a planeswalker reaches 0 loyalty counters, they are destroyed. After you play him, unless otherwise noted, there are no further costs to play his abilities other than the increase/decrease of counters.
Once per turn, on your turn only (starting as soon as you summon him), you can activate one of his abilities as a sorcery (meaning, even if he is destroyed, the spell, once on the stack, will go off pretty much no matter what).
As you can see, you have to choose between abilities and possibly build up enough loyalty counters to activate your more expensive ability.
Now, if a player attacks your planeswalker and you don't stop him/her, it takes damage just like you would. Say you summon Ajani here, he starts at 4 counters so then you choose to activate his first ability. You gain 2 life and he gains a counter moving to 5 total counters. Next turn, your oppenent attacks your planeswalker for 5, you decide not to stop it or simply can't. Ajani then loses 5 counters putting him at 0 counters, he is then destroyed.
Anyways, I hope this has clarified somethings D: