Easiest travel from Brussels airport to Ghent

http://www.belgianrail.be/en/
Tickets are always the same price. Direct trains twice every hour.

Select »Brussels Airport - Zaventem« and »Gent-Sint-Pieters« for departure and arrival stations.
(Use the Flemish spelling »Gent«. The English spelling with an »h« won't bring up the desired result.)

I'd recommend the Zaventem > Knokke train instead of the Gent Sint Pieters if the timing is right. It stops in Ghent on the way, and gets there about 1/2 hour faster. The other one is the local, and stops like 12 times. But, if the timing is not with you, then the extra wait means you come out around the same.

Depending how much experience you have in European trains, you can use the self-serve ticket kiosks to book your trip. You'll need chip and pin, and sometimes one card will work and another wont. Or, you can follow the signs down to the trains, and book with an agent.

The experience advice also applies to whether you want to take the option of hopping the first train to Bussel Zuid/Bruxelles-Midi, and changing trains ( and platforms most likely). In that case Oostende or Blankenberge is the end point. Takes slightly longer than the Knokke option but only about 5 minutes.

Also, you might consider the SNBC/NMBS Phone app. for train information.

the Zaventem > Knokke train instead of the Gent Sint Pieters
That is confusing. The final destination of the train is irrelevant. All connections from Zaventem to Gent will show when using the link given above, including the travel time and whether it is direct or with a change of trains. Choose the most convenient one.

Thank you for the advice, I appreciate all the help.