About buying players.
The first week in auctions is insane. Ppl spend a lot of tokens on average players. If it's your first season, I believe you can build a team of about 85% quality and I think it's enough for you to pick the league trophy. I recomend you to buy players between 18 and 22 years old. So you will be able to use them for 2 more seasons (in general, older players dont grow as faster as those young ones). Anyway, I dont recomend you to spend more than 10 tokens in only one player if you don't plan to buy tokens. It's a limited resource and hard to get it.
So, in resume, if you are in auction and see a player between 18 and 22 years old, 85% or more quality and he's able to be bought with less than 10 tokens, buy it. And, ofc, Don't buy an "AMC" if you don't plan to play with a formation that needs "AMC".
About formations.
I think here in the forum the most used formation is the 4-5-1 V-Style (DL DC DC DR, DMC, MC MC, AML AMR, ST), playing down both flanks. It will bring you great results against teams that have the flanks not well protected. A good variation is to switch the DMC to an AMC, and then you have a 4-2-3W-1, where you can play down flanks or through the middle. So you now have 2 suggestion of balanced formations. Ofc there are other good formations that you can still use: 4-4-1-1, 4-1-2-1-2ND, etc.
About trainings.
I believe that in first seasons your trainings wont be that good. Your manager training level is too low and your training sessions wont bring so much result to the players. But, anyway, try to train the white skills of your players. You have something like 30 advertising videos per day to get bonus. Use it to get rest packs. And spend these rest packs in your young players, to train them hard (rest your player, train him til death, rest him again, train him... etc).
it's useless to spend it in old players, as they grow slowly.