Beat way I find for people starting out is to select your squad by the following
1/ pick all the likely R1 rookies.... All of them
2/ rank them in what you think is job security/ scoring potential. If someone is playing half back flank / distributor, almost a lock. Been shown to be a fantasy goldmine. see sheezel this year as an example.
Mature age players usually are better prospects.
3/ get rid.of the lowest ranked rookies and start selecting premiums. The key here is durability, durability, durability. You won't make a trading mistake if your picks play all games. Also prioritise younger 4-5 year players in this range. Almost always avoid 30+ year olds
Then once in the season, don't be afraid to cut a rookie a week or two early. Then apply the same standards for rookies you bring in and premiums.
There is a whole bunch more to it but after a season or two, you start to get the confidence to back yourself and break the above rules