just for relay no need buy anything at all

1GB RAM 2CPU 50GB+ HDD will do

best options since u need learn are

1. windows + python + relay

2. install ubuntu 20.04 +python

3. install start9 OS (need more CPU RAM)

search internet n learn slowly

LAN relay ws://ip:port

ws://captjwedewdawewdwawdwdwdwd.onion

learn tor install first

for above no need any domain name or ssl

below get clearnet+dns type relay

learn ngix+certbot

plus get get relay.subdomain.io ->ur IP

IPv4 or IPv6 <-- INBOUND any port OPEN(check with ISP)