With an Microsoft Azure free trial, you receive $200 in credits which you can spend on any Azure service, including any virtual machines size you wish to create. Your free trial subscription remains active for 30 days.
You cannot use credits to pay for non Microsoft services like Sendgrid or non Microsoft virtual machines like Barracuda Firewall.
Note that when you create a virtual machine, Azure will start consuming from the $200 credits you received as part of the free trial. Some virtual machines are more expensive than others. It is possible to create items on your free trial subscription which will deplete the $200 credits within 24 or 48 hours. When you run out of credit or your free trial expires 30 days after you created it, your subscription will be disabled.
You may want to check the price sheet here before you go ahead and deploy an item : [Pricing Calculator | Microsoft Azure]. Simply add the items you wish to deploy to get an estimation of how much credits will be consumed.
If you would like to start out your career as a VMware Engineer then enroll for Best Azure Training online