For Bots you want to fully work on one bot a time. And importantly, you’d want to first focus on Golden Bot. There are several reasons for this, particularly that bots are not very effective until further upgraded, and that unlocking bots costs an increasing amount of Medals - which is a scarce and limited currency earned through the Event. For more on the medal event, you can see: Guide to Events & Missions.
Golden Bot: Generally prioritize range, keeping bonus slightly behind, and only consider cooldown for specific Sync strategies.
The reason we are concerned with range first is because we need to make the bot consistent by covering a sufficiently large area. In other words, it wouldn’t help you much if you had a large bonus if your bot is so small that it doesn’t cover a sufficient area where enemies are killed - particularly during your Black Hole cycle.
Once you have maxed or gotten close to maxing range and bonus, you can consider moving to the next bot. It is also worth pointing out that “duration” becomes more relevant if you are not doing a Devo hoarding strategy and also when you have permanent Golden Tower and Black Hole, as then you are more heavily concerned about “uptime” as opposed to having a specific cooldown matching with your econ Ultimate Weapons (Sync).
Amplify Bot: Focus on range first to maximize boss coverage, then improve the bonus for enhanced damage. You may consider adjusting the bot’s cooldown according to either desired farming Sync strategies and/or specific tournament Boss cycles, etc.
Thunder Bot: Maximize this bot for effective crowd control. You essentially need to maximize it in order for it to become impactful.
Flame Bot: Upgrade only after all other bots are essentially fully developed.
This guide is currently a work-in-progress. If you see anything missing you think should be added, Contact me or Submit Feedback. Your contribution will be properly attributed.