About signature campaign
For now better to focus on developing your website. But generally your website needs advertising. I am sure advertising on bitcointalk is much more effective than Twitter and Discord.
Don't worry about spamming. If you hire a good manager, spammers won't partipate in your campaign. There are many big gambling websites that are running signature campaign now or have run it before.
Yeah, the signature campaign part will be the most difficult part if you want to run it by yourself. If you hire someone to take a look at every single message then that guy will make it his job to read every single message of a certain user before they pay them, that way you are leaving a job that is unwanted by a whole team to be done by someone that gets paid for this.
Managers are really worth their money, if you hire someone those guys will spend hours every single day checking messages from the users, you can't hire someone to your team that will do something like this, it would cost you a lot more, but if you freelance it to a manager then you will be at ease. Sure, you can try to do it yourself but you have to ask yourself if your time is more valuable checking messages or doing something else.