How to increase your power level in Splinterlands? Any advice, anyone?

So the season just ended earlier this week and just before the season ended, the screenshot below shows my rating and power level.

So here is the thing, I tried very hard to raise my rating and with some strategizing, patience and lots of cursing, I eventually succeeded. But just being in Bronze II, it is very difficult for me to increase my power given my poor DEC count. I used up more than 60 DEC (which by the way, took me lots of battles to save up) to get my power level to that 2,550 level but after that, I got stonewalled and was unable to reach a higher power level. This is quite frustrating because with that rating, I could’ve easily landed in the lower rungs of Silver III. That would have given me at least 50% more reward chest loots and I guess better pulls too. Heck, I couldn’t even get my rank to Bronze I.

I pretty much stalked peakmonsters until the end of the season but it was nearly impossible to get cards (pick a card, any card) at its lowest price since they were unavailable almost as immediately as they appeared on the screen. This season was quite frustrating because for the first time ever since playing, I qualified for Silver III but my power just prevented me from going there.

I know the most common advice is to “spend some money first”, “don’t just expect anything by playing for free” and so on. I don’t mind spending money but I need to be very careful how I spend my money since my country's currency conversion rate to USD is more than 4x for every USD1. So USD10 is 40++ bucks for me which is like two or three days' meals.

My current approach is to rent the cheapest gold foil card available by refering to the following snapshot chart (full chart can be found at https://docs.splinterlands.com/dark-energy-crystals/burning-cards):

But I think this is not entirely updated as there seem to be some Reward Gold foil card that gives less than the DEC per card than what's shown here (maybe I am just understanding this wrong? or maybe there is a new chart for Reward cards?). Sometimes, if you're lucky and persistent, you can get regular foil legendary for a good DEC which could easily give you 1000 power.

So I am hoping to get some advice or strategy on which type of cards or cards to get/rent that is bang-for-buck/power. Also, how do I increase my power with the little DEC I have (if I need more, then guess I’ll slowly grind up)? This should be pretty helpful for any new beginners too.