It additionally makes a huge difference what you are advertising – casino, poker, bingo, skills, sports – each of these attracts a completely different type of person with different objectives, playing behaviors and spending habits.
Within these groups you have further splits – a blackjack player has different spending behaviors than a slot player etc.
And additionally within each of these groups, the type of promotions you use will influence the type of players who visit your site. For freebies you need much higher visitor numbers to make money than you do for other types of promos.
Then, the look and feel of your site attracts a certain type of person – young males, older females, etc….; looking for adventure, match of wits, companionship, money, entertainment etc…. and so forth. Very different motivators and very different spending behaviors, again.
The more you know about the exact nature of your traffic, the better the projections you can make for your own site.
It can get pretty intricate to try to make any judgements that apply generally. I don’t think it’s really possible, it’s hard enough when one does have a lot of specific data.
As newbie, you also have slightly different objectives than as old timer. If you live in an area and target players where advertising is legal, you can tweak according to the above from the start by designing and purchasing appropriate campagins.
If you are dependent on natural search engine traffic, you do need to try to get volume first, and the visitors have to see your site as something to bookmark because it stood out from the crowd for some reason. You need to build up traffic, get people to come back to YOU for more. Get them to tell their friends that YOUR site offered something different that they liked. You have got to be UNIQUE!
Whatever you do, don’t waste your time and resources buying bulk traffic, 99% of it is fake and will do absolutely nothing for you.