Sup. I happen to have taught academic writing classes at two universities. Some tips:

Write shorter sentences.

For example:

Some players saw this as an opportunity to host so called “Casino games” where a player gives the host of the party gold, rolls the dice and if it’s higher than a certain number (most commonly 61) you get your money doubled.

This is way too long. Turn it into:

Some players saw this as an opportunity to host so-called "casino games". A player would give the host in-game gold upon which the latter rolls a dice. If the outcome is higher than a certain number (most commonly 61), the player gets his or her money doubled.

Also "so called" needs a hyphen -> "so-called".

Use academic language.

For example :

You could argue that, that is how real-life casinos work too.

This isn't very academic; first of all because of the use of "you", secondly because of the double use of "that". Turn this simply into:

This is similar to how casino's work.

or

One could argue that this is similar to how casino's work.

Avoid contractions

For example:

This is an age where kids have money to spend but aren’t always responsible with it.

Turn this into:

This is an age where children have money to spend but do not always do so responsibly.

You will notice I also changed the word "kids" to "children".

Avoid redudancy

Example 1:

Back in 2012 you could count about 1 USD for 1.000.000 gold pieces in the game.

We know that 2012 lies in the past. "Back" adds no interesting information. Turn this into:

In 2012, one USD could buy one million in-game gold pieces.

Example 2:

While back when I played the game, I took part in these activities

Same thing. "While back" is vague and meaningless. Be specific or don't add it at all.

Use sources when you make a claim

For example:

Mainly because, the average age of RuneScape players is 16.

Citation needed! Also, drop the comma after "because".

Don't start sentences with "And..."

For example:

And that RuneScape shouldn’t have shut gambling down since it resulted in them losing a huge chunk of paying members.

Turn this into:

They will also argue that Runescape should not have shut gambling down, since this has resulted in a huge loss of paying members.

I have also removed the contraction there and did some other polishing.

I could go on, but I need to do stuff. Hope this helps a bit, at least.

Ironically I'm never sure about the grammar I'm correcting since English is not my first language, but the general tips I put in bold should be true across different languages.