I just read interesting advises about how to design good PCBs. But they apply mostly to a professional consumer electronics. PCB is not so critical for a DIY person. Maybe if your board uses Gigahertses, you should be awake when you design it.
Examples
A friend of mine left out all the power supply capacitors of his STM32L0 board. He added only those what were absolutely needed.
I once forgot to connect one power supply +5V pin of Atmega2560 CPU. The board worked fine, until there were assembly problems elsewhere on the board and I found out this too.
I once made a low power 144MHz crystal controlled FM transmitter on a perforated board (Veroboard). Power and ground were 1-2 inches apart. The thing even worked.
But still I usually route power and ground first. The rest is less important.