Gimp is a smaller version of Photoshop which is recommended for the people who just started making signatures because it has a user friendly interface.
But if you want to go "deeper" with all the effects and everything , you need Photoshop.
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The signature is nice but it's too "empty" , there's a render , a background some text and a 8-9AM light .
For your first signature it's good , but for the next ones ( if there are going to be others ) stick to tutorials.