This is a picture of the top bud on my 1st grow, how does it look so far? How much longer should I let it grow? Any other advice would be greatly appreciated thanks.
Your plant looks good. I am still pretty new to growing, but here are a few thoughts and questions for you to consider...
The best way to determine when to harvest is by examining the trichs on the buds. Pretty hard to do by eye, so a lot of folks get a magnifying glass or jewelers loupe to get a close-up. Another option is an inexpensive microscope that connects to your computer. As the plant gets closer to harvest, the trichs will gradually change colour, starting out clear, then cloudy, and then amber. You can target your harvest based on the colour that you want. Of course, I can't see the trichs in the photo that you posted.
Here's a trich shot from my last plant, just when I harvested it:
It can be a bit tricky, or at least it was for me, to determine how much cloudy versus clear there really is, so I found posting photos for other to take a look at really helpful. The pistils (the white hairs) will usually shrivel up and turn a darker colour when harvest is getting close.
My guess is that you are still several weeks away from harvest, but be sure to take a look at the trichs, and ask for some other folks' opinion.
In my signature there is a really interesting article from DJ Short about harvesting as well.