Software level raid for esxi inside the same host is almost non-existant. Hardware raid is the straightforward "affordable" way to go, just make sure to verify the card in the compatibility matrix and you should be golden.
If you don't need any redundancy, you could do a 1-host vSAN via CLI. But 1 SSD will be 'lost' to being a cache drive (should use a higher DWPD type drive (preferably 3-10 DWPD)), and if 1 drive fails, assume you lost everything.
Personally, unless you want to create a single disk for a VM that's larger than your largest storage device, I'd just go with multiple individual drives w/o raid and spread your VMs or your VM's disks across the multiple drives.
If you want redundancy, I'd suggest to look at a proper hardware raid controller (e.g. LSI or Adaptec solution).