Just before contributing I believe I should became a user for this product. But the last time I tried Rakudo I found myself in struggle just because of lack of documentation.
When I say 'documentation' I actually mean the full chain of 'quick getting started', 'the complete user manual', and 'internal architecture/design for hackers'. All I saw before was the type one of these, how to install and run the fresh-built binary. Yes I understand that the code itself is not yet done, but this fact is not a blocker for documentation process. I believe this needs a huge effort from developer team and especially project leads -- take as an example the OpenBSD project -- they refuse any changes if these changes are not documented.
Resuming -- no how-tos, but the complete manual is needed to gain userbase and only after that the part of it maybe became your contributors. This is just my opinion, hope it helps.