Wow... It's not a small task that you're asking for, the whole core mechanism of your future game. But in the same time, there's a really simple answer that can be gave: Be curious and look around.
All the points in your question have been answered multiple time in this part of the forum. The navigation part by example
have been covered yesterday, and it cover the interaction part as well. For the money, it
have been addressed last Friday. It's been a little longer that no one asked about a time system, but there's dozen of threads about this.
Of course, all this is independent and not explicitly part of a "system". But it's better like this, really.
I mean, the "money" part is the most basic thing possible, yet you had to ask, what mean that you've near to no knowledge regarding programming. By itself it's not a problem, but if you go for the use a big all in one system, you'll be overflown by information that you don't understand. Then, it would need just one small problem for you to be totally lost and facing a now useless code.
A least small independent parts are easier to understand and to handle. And if there's a problem somewhere, it will just break a small part of your project, what is easier to deal with.
