Should I focus on one crop to get my knowledge of it up, or is diversification the strat?
good question!! the answer is... complicated. even with many playthroughs, i myself have not found a perfect way to do this. you want to both get knowledge up, but you also want a variety of crops - how to balance it?
first, use ollas. the main obstacle to having a lot of crops (and therefore being able to have a pretty good variety while also getting knowledge) is watering. even with a well, it can be tedious. ollas water the 8 adjacent spaces automatically every morning. and remember, you do not need to top them off every day! the olla will last 2 days, and will visually show the water level going down; the last day will show the crops watered and olla empty - this is when you need to refill it. you don't need to spend your time and energy topping it off every day!
second, upgrade that waterskin! in some farming games, like stardew valley, the watering can is not that important to upgrade. that is not the case in RoP! upgrading your waterskin will mean your reach will drastically expand for less energy, and you will refill the olla in less trips!
i go into all this bc having your watering be easy makes it much easier to both diversely plant crops, and plant a lot of them, so you are able to get the best of both worlds. the soil in RoP does not become untilled over time, so you are able to set up crop fields easily, with watering being the only ongoing concern, energy-wise
now i don't know how everyone does this, but my general strategy is, in year 1, to use the smaller northern field for crops, and the southern field for animals. animals will not only eat grass, but also weeds/fiber, helping clear that area. meanwhile, im able to focus on filling the top field with crops.
i usually do 2-3 ollas for each crop. if a crop grows into the next season, i may chop it down to 1 olla, to make room for crops i haven't grown before. at the end of year 1, i will check how far each crop is in knowledge, then in year 2, will prioritize the crops with less knowledge. for example, if tomatoes are at level 5, the max, then I will only plant 1 olla of them, but if they're at level 1, the lowest, i might plant 3-4 ollas of them.
but also, i will plant a lot of a crop if i know i want to process or contribute a lot of it, even if it's at max level. so i have to balance that, as well.
in year 2 is when i may rearrange the farm and fields for whatever vibe im going for (which changes in every playthrough), but my year 1 layout is generally this, bc ive found it works for me.
there is not a perfect or right way to do it! the only thing i can say for sure is what not to do:
do not only plant 1 or 2 crops, and do not skimp on planting crops in general.
having a variety of crops is important, and having enough to contribute is important game progression!
sorry i can't be more exact on how to do this - it really is something that everyone does differently! ive seen some people meander through it, only planting an olla for each crop, taking until year 3 or 4 to get levels up, ive seen people go all in on one, with only a few plots for others, getting max level for certain crops extremely fast - it depends on what you want to do. and as long as you're having fun, it's good!