Game supplied bikes are a bottomless pit of wasted money.
Upgrading the components will soon start to outweigh what you paid for the bike.
Full suspension bikes could be a bottomless pit as well, the real entry level ones weigh a ton and they come with some real crummy rims and front forks, not to even go in to the rear shocks #crappystuff
Look at a bike with discs, and here you want hydraulics, going cable activated discs with the mind of "upgrading" at a later stage, will again cost more from the word go.
If you buy a bike with rim brakes, again be very careful, you can't just slap on discs.
You have to see if the frame and fork have disc mounting tabs, first and foremost.
Then look at the hubs, are they disc hubs built on to disc rims ?
If this is the case, you are a tad better off.
The new Alivio stuff is 9 speed now and very good, actually quite damn exceptional.
Wait for the new Silverback stock to land towards end November, great value.