[What criteria should be followed to get more orders?]

More gig marketing 

[how to get order]

More social media marketing more orders.

[Are Fiverr profiles linked with forum?]

If you are active on fiverr forum, that means your gigs are active

[Best way to grow a fiveer gig for selling discord servers]

Exactly there are no anyways without gig marketing to get more orders

[not getting orders]

Why I'm not getting any order since I got two orders?

[How can I grow my gig impression and click?]

Just do marketing more and more .if you do, definitely yours will be increase.