Look at buying summoners. Such as Rotwell and Shhine if you can.
Try and pick a splinter or 2 and build them first. After a season ends the available reward cards flood the market that day and generally drive the prices of those cards way down which is a great time to buy.
Good luck
Nice thanks! I noticed the prices were going down for some cards. I thought it was due to the new releases having more cards minted. But it makes sense the rewards will contribute.