You will get loads of different answers on this one and I can tell you what I am using but that doesn't make it best for you
There are people using photoshop, canva, paint, gimp and any other photo editing software.
Make sure to read this post for a guidance of the sizes of the banner. There's also more info in that post that might help you out!
Make it simple yet attractive.
I'll have to agree with what @itstom has mentioned. I myself use photoshop elements 15 along with a copy of the YouTube Channel banner template that you can find with a google search. I just took a look at your channel and all I know from what I have seen is your a Travel channel. Consider adding a "What your channel about message Keep it brief. You might also want to include a posting schedule for your videos.
Just remember when creating a banner, using the YouTuber Banner Template available out there, take into account the position of the channel logo on both a browser and mobile. You don't want your logo blocking parts of your banner by mistake.