I am lucky enough to own 2 fight sticks, both of which I built myself from scratch. One contains a square gate the other an Octo.
To be honest, I am now used to both but I feel that the Octo is easier to get the hang of and would recommend an Octo to anyone moving from a pad to a stick for the first time.
As many people have mentioned, it is all down to personal preference. A Sanwa JLF will come will a square gate as standard and an Octo gate will only cost you 5 or 6 quid so buy one and try both. They are very very easy to swap over. That way you can decide which you prefer.
In terms of buttons - stick with Sanwa or Seimitsu they are the best and most hardwearing/ duarble and sensitive. Seimitsu ‘skeleton’ buttons are useful if you wish to incorporate your top panel artwork as they are clear
In terms of button layout on your top panel, well, that’s totally down to you. There are so many layout options such as Japense Arcade layout, American Arcade layout, Sega layout to name but a few.
Do you want 6 buttons on top or 8?, Do you want your guide and start on the top, side or back panels?, Do you want to wire up the ‘Back’ button (360 only)??, Are you comfortable with LT and RT soldering (adding resistors to a PCB)??
These are all things you will need to decide upon before the build begins.