Some advice indicates not to have a profile unless there is some investment.
Not sure about the investment to be honest. It could be good for investors to check when you ask them for funds. I would do it, BUT I would hold on announcing a round of investment on AngelList until you have at least half of it. That's my advice, I hope it helps!
I have found that AngelList is a great place to potentially find your first round of investment due to the social aspects of the network as a whole. The ability to connect with investors and subsequently message them allows you to network with individuals whom may take an interest in your company and become that first angel investor.
I don’t believe there is any harm in creating a profile on these online platforms before being funded. But in my experience you are not likely to get much traction with investors there unless you first: (1) have a lead investor you have met with in person who is in for 5% to 10% of your round; or (2) have established connections with investors who can promote your deal on these platforms. Investors want to see some kind of preliminary due diligence on you and your deal before they commit.