Any tips on how to gain growth from a Product Hunt launch?

To add to the other post. Assuming you make it to the top 15 or so, expect a big peak and then pretty quick decline over the next few days. It's not a sustainable source of traffic.

I've launch 3 in the top 10 (i think).

Some quick tips
Make sure it works. It doesn't have to be perfect, but you don't want it to completely fall over. I actually like Product hunt as a way to quickly get people stress testing my app and finding what breaks.
I don't rely on it generating enough sign ups to sustain the business.
Know that they probably aren't your market. It's more to validate it works, if there's interest and potentially as a lead to other interesting opportunities through networking.

It will generate some traffic over time. Just because PH ranks well and has users. Not enough to sustain the business. But for specific keywords.

Make sure you have someway to keep in touch with customers. Email signup, some kind of content they can download etc

Ideally - have a paid plan. If you can actually get people to start paying that's really what you want to validate. But again PH probably isn't your perfect audience so don't use this as a way to decide if the business idea will work or not.

just my 2c

It's worth having a look at what others have posted about Product Hunt, there's plenty of stories and advice shared.