Reputation requirements vary by site type, and sometimes between sites. In general, the following categories of StackExchange sites will have similar rules:
- Private Beta will have very low reputation requirements so that participants who have committed to the project can help quickly generate content for the site before it opens to the public.
- Public Beta (the current state for this site) has moderate-to-low requirements that ensure users will need to earn a certain amount of trust from the community before gaining certain privileges, while still accommodating to the fact that the site is still in its early stages and reputation will be generally harder to earn at this point.
- Graduated Sites have the highest reputation requirements to help maintain the quality standards of StackExchange on sites which have been deemed to have long-term value.
- Meta StackOverflow has special rules because it is by nature very different from other StackExchange sites.
To check how much reputation is required for a specific action, and see where you stand with regards to those requirements, go to the /privileges
page on any main site. Here, that would be https://codegolf.stackexchange.com/privileges.
To find out how reputation is earned (and how it can also be lost), check the "What's Reputation" page of a given main site. Here, it's https://codegolf.stackexchange.com/help/whats-reputation.
To answer your questions specifically...
Asking and answering questions on the main site, also called "creating posts" requires only 1 rep. New users with zero history on StackExchange start with 1 rep, so you should have no difficulty (in terms of permissions) with performing these actions. Just make sure you're using the proper UI and, for example, not trying to submit a comment instead. The only limitations to this is that brand-new users cannot answer "protected" questions, or create posts "too rapidly".
Commenting on your own posts, or answers in your own question thread, is also available to all users.
Participating on the Meta site requires 5 reputation. This is a nominal requirement, which is easily met, to prevent spam on the Meta site.
To shake off the "new user restrictions" (which include the aforementioned limitations against answering protected questions or posting too quickly) you need 10 rep. Again, this is a very small amount which is easily earned, and this restriction is primarily just a spam prevention mechanism.
To leave comments on other people's posts, you need 50 reputation. This serves the dual purpose of preventing spam and (hopefully) demonstrating that you have at least some idea of how the question/answer/comment system works (and when it's appropriate to do - or not do do - any of those actions) before you're fully cut loose to comment everywhere.
These standards are among the few which are the same across all sites, regardless of their stage in the lifecycle.
Getting to Meta can be accomplished by any one of the following (or some mixtures thereof):
- 1 up-vote on a question you post
- Accept an answer on 3 of your questions
- Approval of 3 of your edit suggestions
- Note: You can always edit your own posts, and I believe any user - even down to 1 rep - can suggest edits to others' posts, but editing other people's posts autonomously is not granted until much later.
Passing out of the new user restrictions can be done by:
- 1 up-vote on an answer you post
- 1 of your answers is accepted
- 2 up-votes across questions you've posted
- Accept an answer on 5 of your questions
- Approval of 5 of your edit suggestions
Gaining "comment everywhere" privileges can be achieved by:
- 5 up-votes across your answers
- 4 of your answers get accepted
- 10 up-votes across questions you've posted
- Accept answers on 25 of your questions
- Have 25 edit suggestions approved
- Get a bounty awarded manually to 1 of your answers
- Note: Minimum bounty amount is 50 rep.
- Get a bounty awarded automatically to 2 of your answers
- Note: Auto-awards of bounties only award half the bounty value and require two up-votes on the answer.
General Note: The above assumes you have not lost any reputation (e.g.: by getting flags or down-votes on your posts) along the way.
All of the aforementioned restrictions (except editing other people's posts) can be bypassed if you already have at least 200 reputation on any other StackExchange site, and you make sure to associate your account here with the other site's account. That will give you an automatic 100-reputation boost.
All of the above actions must be done on a "main site". With the exception of Meta StackOverflow, participation on Meta does not earn reputation. Your reputation and privileges on a Meta site generally mirrors that of the associated main site.