As Kurund pointed out, the general instructions are at https://github.com/civicrm/civicrm-buildkit . Follow those instructions to download the all the tools.
There are a few details that may not be well represented yet in the documentation:
As the main developer behind buildkit, I use it mostly in MAMP (and a bit in Debian and Ubuntu).
Buildkit runs ...
This may indicate that either:
The PHP runtime is missing the PDO or MySQL extensions. This may help: https://wiki.civicrm.org/confluence/display/CRMDOC/Setup+Command-Line+PHP (At time of writing, I'd avoid PHP 5.6 for CLI dev -- GenCode may have issues with it.)
The DB settings haven't been configured (e.g. the step for running amp config was skipped).
I haven't experienced this myself, but -- skimming the code in index.php -- it appears to track a variable called civicrm_install_type. The variable defaults to drupal but can be set to wordpress by passing ?civicrm_install_type=wordpress. Once it is set, it's stored in the SESSION and reused for future page-views.
One way you could probably trigger this ...
The URL looks off to me. The link to the dashboard should be /civicrm?reset=1 and to the status page /civicrm/a/#/status. /civicrm/a/ is not a page and I also get "Unknown path" when navigating there in a Backdrop install. Perhaps check to see if your URLs are being rewritten in apache?
Here's an example wp-cli command I use that works:
/home/ubuntu/wp-cli/wp-cli --require=/home/ubuntu/wp-cli/civicrm.php --path=/var/www/wordpress civicrm api job.execute > /dev/null
I hope that helps!
UPDATE: I see your problem! "/path/to/wp" means, "path to wp-cli, including wp-cli". I completely looked past that part at the beginning, since that's ...