A signature is your consent or proof for others that the document or anything is accepted, approved, known and acknowledged by you. Thus it is a prima facie evidence that you know or accept the terms and conditions as mentioned in the documents and know about it.
There is no fixed rule for a signature and it can be in any form, any language, can be mixtures of cursive and print, can be scribbled, can be clear and legible, can include your entire first and last name or full name, it can be messy or curly, etc. There is no single rule for a signature.
The point that one needs to remember while making a signature is that you should be able to write and reproduce in the same formate whenever and wherever required. Before finalising to a signature, practice your new signature several times until it comes out naturally while writing or signing and check if it can be easily reproduced by you or else, you need to simplify your design or style or complete signature.
One point you need to keep in mind while before making it official or legal by signing it on all your legal documents like mark sheets or certificates, bank records, driver's license, passport, pan card, aadhar card, etc, make sure that you can reproduce the signature as it may be troublesome to change it later. As these documents serve to identify or acknowledge you if the signature doesn't match, it can arise suspicion and cannot be accepted.
Now, as you have mentioned that every document of yours have only your first name, it stands valid and is acceptable on every document and everywhere but always make sure that you keep or put your same sinature on every documnet as mentioned.
“The most important thing in life is to learn how to give out love, and to let it come in." — Morrie Schwartz