Is this gun I've bought any good?

Quite simply, by the time you have bought the gun it is a little late to ask this.

If you are looking for purchasing advice, ask in the general chat and provide as much information as possible about the use case and what style your are looking for. A general rule of thumb though is G&G Combat Machine if you want an entry level M4, and Cyma if you want an entry level AK.

If you are looking for upgrade advice, post a topic in the Tech Talk section and you can get advice there. Make sure you include information about what you plan to upgrade and what you’re trying to achieve. A budget and idea of how comfortable you are taking things apart is also helpful.