Publish it on arXiv.org or ECCC (Electronic Colloquium on Computational Complexity). Then, check whatever you have published on arXiv is novel, then submit to a 2nd/3rd tier conference.
That order is no good. You’d want to check what other people have done in that area before you spend weeks figuring out the details of your idea, let alone produce a decent paper and publish on the arxiv. Not to mention that the arxiv is for preprints, not half-baked ideas.
Step 3 is absolutely correct.
I agree that the order of Step 1 and 2 should be reverted, but how is Step 3 absolutely correct? The tier of the conference you should submit to depends on the content of the paper, not on the author/affiliation.
I don't think anybody's first paper will be accepted at a tier 1 conference. It takes practice to learn how to write a paper, not just in style but also the substance. In academia, your supervisors will typically help/guide you. It's going to be much harder on your own without any experience.