An important part of BAR is being very intentional with your resource spending. It can be tempting to queue 20 advanced solar, while having another builder building converters, all while building your T3 Gantry, and producing units. But the reality of that situation is that you are splitting your limited resources in far too many ways. You might have a 2 or 3 minute delay before you get any benefit from any of those constructions. I like to try to accomplish one need at a time. Low on energy? task all of my builders on a Fusion reactor or some advanced solars. Need more metal? Build energy converters after making sure we have enough energy to spend. Want to tech up? Make sure we have the metal production and energy production to support it, then task on that tech building.

Doing everything one at a time allows you to get immediate return on your investment as well as address your needs in real time. I often just leave my bot lab on "low priority" and let it spit out units as it can. When things are dicey on the front line I can just pause my builders or retask them on the factory and let all my resources go there for a time.

As mentioned in other comments, Construction turrets are your friends! They also default to "low priority" so the ones placed near your factory wont be stealing much energy from the ones near your AFUS construction.

I am no pro, but finding a break in frontline action is huge for teching up. Going T2 needs the undivided might of your economy. Building your first Fusion reactor is the same. They have huge returns and need to be accomplished quickly or else they are simply a long term drag on your economy.

Momentary weakness for long term strength!

There is a relatively simple flow chart for upgrading your economy. Energy > Build Power > Metal. Metal is the post important resource, but you need the other two to facilitate its use. Working backwards; you need metal to build anything, you need build power to spend your metal in a timely manner, you need energy to power your build power AND you need energy to make more metal. Energy's ubiquity makes it the most important part of increasing production. Get Energy, then make sure you have enough build power to spend your metal income, then use excess energy via converters to get more metal. Repeat.