You should make your project listed in some ICO listing site. your website, ann thread and bounty tread must be on famous cryptocurrency related website, so it can be good to outreach potential investors. Launch an airdrop is also good, make many people join your bounty campaign and airdrop by give massive rewards, usually successful project has many supporter. Signature, Facebook and Twitter campaign is very good to spread the word about your project, I suggest you to hire campaign manager to manage your bounty campaign and airdrop because if the participants is too many then you will not be able to do other thing important such as manage other advertisement beside bounty campaign and airdrop. Usually CMO of a project will put many advertisement/banner in famous website, hire people to create promotional videos, partnering with famous youtubers, and do some offline advertising by joining some business event or go to big companies directly to get big investors.
Promote a project is not a simple thing, it's not limited on bounty campaign and airdrop.