you should use VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT if you only want to submit the command buffer once. For example, every command buffer you record once per frame, submit, and then reset its command pool after waiting for the fence, should have this flag. On the other hand, command buffers you record once but submit multiple times, for example post processing, should not have this flag.
VK_COMMAND_BUFFER_USAGE_RENDER_PASS_CONTINUE_BIT is only useful for secondary command buffers, it is ignored for primary ones. For secondary command buffers this specifies execution inside a renderpass and you need to specify renderpass inheritance if you specify this flag. Its usage is pretty specific, so generally you do not need this flag.
VK_COMMAND_BUFFER_USAGE_SIMULTANEOUS_USE_BIT says that you can submit the command buffer multiple times without waiting for the previous submit to finish via a fence. Normally you should at least double-buffer your multi-use command buffers so that you would not need this flag.
If you just want to render a static triangle on your screen, you can create one command pool and two command buffers without any flags at app-startup, record the rendering, and then ping-pong: fence-wait, submit.
Or, you could have two command pools with one command buffer each with flag VK_COMMAND_BUFFER_USAGE_ONE_TIME_SUBMIT_BIT, and then ping pong: fence-wait, reset pool, record, submit.