I'm sure there are really good guides out there but I think it helps if you have ever played Yahtzee? It's a dice game a lot of people love and really similar concept.
Once you get used to it I bet you'll love it. You just have to think about the odds.
So yellow and red are the most commonly rolled, then green, and purple is rare.
So what I do is roll and see what I get. Say I got three reds, a green, and a yellow. I could score for the reds box (jumbleberries), since I have three of them. Or I could score for the three of a kind box, since I already have three reds.
But I still have two rolls left, so I ask myself how I could improve my score in either category. If I rolled another red, I could score (select) the four of a kind box instead, and I have good odds of that since red is the most common to roll. Or the points could just go in the reds box (jumbleberry). Either way, maybe I decide to go for more reds, so I click on the 3 jars with red to save them, and then click roll again. Then the two final jars re roll. Let's say I am lucky and get two more reds! So I could now score in the five in a row box! I would probably decide to do that, since it's hard to get 5 of one color. So I wouldn't use my 3rd roll.
Then it starts over. Maybe this time I get 2 purples, a red, and 2 greens. The purples are rare and lots of points. So again, I have to decide what to try to roll for... I could save the two purples and roll the others and try for 3 or 4 moonberries.
Or, I almost have all the colors, which would work for mixed basket. All I need is a yellow, which is a fairly common roll. So maybe I keep one purple, one green, and one red and roll the two extras hoping for a yellow. Does that kinda make sense?