Had issue when tried to build own nextcloud box

I’d like to setup nextcloud box. I didn’t have WD PiDrive. Instead I tried to use a MicroSD card instead of PiDrive. My issue is that after I flashed ubuntu-core-16-armhf-rpi3-installer-20170329.img to MicroSD card on windows. Then plugged the MicroSD card into Raspberry Pi 3. And connect Pi3 to power. I saw the lights start to blink, red and green. I waited over 20 minutes. Looks like it did not boot up. Because I connected to display (TV) with HDMI. There was no single on TV.
My questions:

  1. Can I build own nextcloud box without WD PiDrive? If yes, how can I build it?
  2. Does Pi3 support to connect to HDMI? Already flashed ubuntu-core-16-armhf-rpi3-installer-20170329.img to MicroSD card.
    1. Can I build own nextcloud box without WD PiDrive using ubuntu-core-16-armhf-rpi3-installer-20170329.img instead of nextcloudPi image?

Thanks for your help