There are books and books about good practice in data visualisation. It sounds like you're showing detailed data to audiences who are highly engaged in the data in a dashboard-like context, so I'd suggest Information Dashboard Design by Stephen Few - the latest edition of which includes design for mobile devices. It's a good book with clear practical advice.
(be warned though that Few is one of these authors - common in info design - who sees his advice and preferences as holy law; 95% of it is good, solid advice based on sound reasoning and solid principles, but do take his hyperbole with a pinch of salt)
But here are some general principles to get you started:
- Know your audience: how much they know, and how much they know what they're looking for. Structure your information so users see things that are clear and relevant for their level of expertise, then can follow a path down to each next level of detail as they find points that are relevant to their interests
- Small, simple charts side-by-side on the same scale which are easy to compare side-by-side and also look at one at a time ("small multiples") are generally better than complicated many-variable mega-charts where you spend more energy decoding the chart than interpreting the meaning of the data.
- Have a clear, clean visual hierarchy where the things that show the data stand out most strongly, with minimial clutter and distractions, and any gridlines, labels etc that are absolutely necessary subdued and made less prominent. Only add decorative elements where there is a real, practical benefit in terms of helping users understand and interact (for example, setting context for less informed or less engaged users, making key features eye-catching to users, or highlighting key details).