Is there a particular pillow I should buy for my toddler. It will be his first pillow and I am unsure on what brand/type/make.

Red Nose does not recommend any brand or type of pillow for a toddler.
How old is your toddler? Is he in a bed or still in a cot?

Red Nose does not recommend the use of a pillow until baby is in a bed & is over 2 years of age.
https://rednose.org.au/downloads/RN0407_22_Cot-to-Bed.pdf  (see P1, column 3)
https://rednose.org.au/article/at-what-age-can-i-introduce-cot-bumpers-and-pillows