Generally, the shape is round. Although square seals are equally effective, circular seals are more mainstream.
Any diameter, generally10-15 mm.
There is no prescribed difference between men and women. Generally, men will be bigger and women will be smaller, but it will not affect the effect.
Be sure to engrave your full name, which is called "real seal" in Japan and has legal effect; Only the surname is called "seal recognition", which only has the internal effect of companies, schools and other units. Choose a font that looks good to you, there is no limit.
Ink should be available at any time, but it is sold in the hundred-dollar store, so you don't need to bring it.
Stamping is valid on all occasions, and it is also valid to stamp only the surname on internal occasions. If you are too lazy to distinguish, it is ok not to distinguish.
There is no need to carve traditional Chinese characters. In fact, Japanese documents can now be registered in simplified Chinese, but transliteration will lead to complications. My ID card, student ID card and insurance card are all simplified characters.