I don't want to install the Budgie Desktop Environment to avoid bugs and endless tweaks. Specifically, I like the Transparent Top Panel and the Icon pack. Is there a Budgie theme for Gnome?
Try the following.
Change your application theme (GTK+) and shell theme to Arc (preferably "Dark" or "Darker" variant) using (GNOME) Tweaks. To install the theme on Ubuntu 17.10 and later from the Universe repository run
sudo apt install arc-theme
Ubuntu 16.04 requires adding the repo
sudo sh -c "echo 'deb http://download.opensuse.org/repositories/home:/Horst3180/xUbuntu_16.04/ /' > /etc/apt/sources.list.d/home:Horst3180.list" sudo apt-get update sudo apt install arc-theme
Change your icon theme to Moka. For Ubuntu 17.10 and later, it's available from the Universe repository, the
pocillo-icon-themepackage will install the Moka and Faba icon-sets
sudo apt install pocillo-icon-theme
On older Ubuntu releases, install them from Sam Hewitt's PPA by running
sudo add-apt-repository ppa:snwh/ppa sudo apt update sudo apt-get install moka-icon-theme faba-icon-theme faba-mono-icons
Make the Ubuntu dock (on Ubuntu 17.10 and later) flexible following this Q&A: How can I stop Ubuntu Dock from extending to the edges? Also perhaps reduce the size of app icons in the dock from Settings > Dock.
For earlier Ubuntu releases, use the GNOME shell extension called Dash to Dock.
The top bar in GNOME has dynamic transparency feature nowadays by default. If you want to have more control over its transparency use the Dynamic Panel Transparency extension (see this for reference).