You can get started on any hardware you have collecting dust. Install start9 on an old computer. or buy a cheap desktop from ebay you'll spend maybe a bit over $150 on a computer and an SSD. 

there are other oneclick install platforms like yunohost and sovran systems that help you get started selfhosting. 

Also start small mabey just spin up something like a password manager or some picture backup like immch. get used to using it and keeping it updated. no need to dive off the tech deep end and host 100 things until your ready.