I'm looking for a good MMO that doesn't have membership, has low specs, has a lot of people playing and is playable on both Mac and PC. I used to play a lot of wizard 101 and it was lots of fun and I would play it again although I do not want to pay for membership. Any suggestions?

Swagepi : Is there anything in particular you are looking for in an MMO? I don't want to suggest anything if its not what you're looking for.

I'm able to run Marvel Heroes 2015. I've heard it needs good specs, but mine are awful.
Anyways, the gameplay is pretty fun as long as you have friends. It gets a bit grind-y if you don't have anyone to play with.
I also recommend the browser MMO "Monster Ranch". It's like Pokemon with several MMO features integrated.

I would Definitely recommend Mabinogi. It wasn't very popular when it first came out, but now it has new classes and a ton of other new stuff, and it's full of really nice people. It meets all of your recommendations. It's a bit different from your average MMO. You can gain exp and level by doing tons of non-combat things. If you want to be a merchant, you can do that. If you want to be a Tailor, sure. It's more than a combat MMO, it's advertised as a Life MMO. Sure, combat is a big part of it, but there's SO much more you can do.

Also, another thing I love about it, is that it's skill based, not level based. The more you use your skills, the better you become at them. Well, for most skills. Some skills can only be leveled up by reading certain books. You can solo some really tough dungeons by using your defense and counterattack skills at the right time. Trust me, I mostly solo, and I rocked most dungeons.

There is a main story quest, and those give you tons of rewards that are worth it, but later on they get ridiculously difficult. At that point, you're going to want some pretty powerful friends. Joining a Guild is a pretty good way for some help with those. Most people are either super friendly, and willing to help, in my experience.

When you start out they give you a detailed description of all the races and classes. Some classes are race specific. However, you can use physical and magic classes of all the races. Humans, Giants, and Elves. 

As for some of the classes, they have tons... No joke. There are even non combat classes. I just remembered the classes are called Talents. They're also divided by genre. Like Life Talents, Combat Talents, and Beginner Talents, ones that are recommended for Beginners. You should start with one of those, I'd recommend Close Combat, to get you used to the basics of physical combat. So, here are just a few of the Talents:

Combat Talents: Close Combat (Swords, axes, maces, shields), Magic (staves and wands), Archery, Battle Alchemy (Arm mounted guns that consume elemental ammo), Martial arts (One of the best pvp fighters and great at pve, but there's a glitch that makes your character useless for the whole dungeon... This was my main... And it sucked. It was fun, but I do not recommend it.), Music (any instrument, to buff or debuff. You can also use score scrolls to create or play songs.), Puppetry, Ninja, Gunner, Lance Combat, and Transmutation.

Life Talents: Adventure (MY favorite, uses Dowsing rods to discover ruins, treasure, or secret dungeons), Mercantile, Holy Arts, Cooking, Smithing (Recommended if you want really good armor and weapons for much cheaper. It takes some time though, but it'll save you tons of money.), Tailoring, Medicine and Carpentry.

Also, regardless of whichever class you pick, you can still use magic. So ALWAYS get the Heal spell. It's the best.

Each Talent comes with a Tutorial of how to use the Class effectively. You just have to find the Beginner's Board in every town. It's easy to see.

Wow, that was long. I really hope this helped you.

Oh, and also Mabinogi is 100% free. They also have holiday events every year. Fun stuff. 

I hope you give it a try, it's one the best free MMO's I've ever played. Enjoy!

A really good MMo (in my opinion) is Star Wars: Old Republic. It has some limitations on it, but it's really open. Plus you have 6 classes to choose from each with a unique story line! It's one of the best I've played. Another I would recommend checking out is: 

Unturned. It's a Minecraft style game, but it's unique, and hard to explain... (It's an FPS game though!) 

MADDMASTA : I'm looking for something that is more combat based and isn't anime-esque and has people playing so i can find people to help me quest. It can be a 2D game or 3D, it doesn't matter. I am also looking for an MMO that isn't pay to win. I used to play MapleStory a lot too and liked it although the more you level the more pay to win i gets and it is dying. Also, Archeage looks like a great MMO although I can't run a 40 gigabyte game on my craptop. I'd also like it to be on Mac and PC.

F. Starr : I'll try it out although I don't really like the whole anime romance theme.

Swagepi : I would recommend Path of Exile. It's a free-to-play 3D action MMORPG, has no micro-transactions (other than to make your stuff look cooler, but doesn't affect actual gameplay), has a large player base, is 5 GB and supposedly supports every day laptops. The only downside is no support for Mac.

I HAVE played it, and I loved it. Definitely worth a try in my honest opinion.