From a UI perspective, message counters on the home screen or app drawer icons would be redundant since all your notifications are visible, counted, and accessible from the status bar and notification tray. Although I think a visible counter for individual notifications on the status bar would be nice so we can remove that extra step in pulling down the notification tray to see how many messages you received.
As far as Gmail is concerned...since the 2.3.5 update, Google has "fixed" permissions in the gmail client that prevents third-party apps from accessing it. Thus any third party widgets or message counters will no longer work with Gmail. They did this, apparently, for "security" reasons.
There are workarounds to the gmail permissions fix but it requires root access.
[App] Patched Gmail to fix Go Notification and other widgets - xda-developers
There are some other notification counter solutions...
You could always try NotifierPro
https://forums.androidcentral.com/e...nlucas.notificationtoasterlite&token=diOqWX0p
It gives you a semi-obtrusive banner that works with Gmail, Google Voice, SMS, missed calls, and a host of other apps. It can be positioned at the on-top or right below the status bar, in the middle of the screen, or at the very bottom of the screen. The only thing is that it only displays the latest notification(s) you received one at time a time until you swipe it away to view the next one. It does count as well.
There are other solutions such as lock screen replacements and/or widgets like Executive Assistant (which can work with Gmail).
https://forums.androidcentral.com/e...s?id=com.appventive.ExecAssist&token=SUkPXAfh
The only thing is it's pretty pricey for an app. :-\ There's a free adware version but you can't use the widget in that one.
I'm sure there are some others out there but I haven't really tried them all.