While it is getting old and a little outdated it is still a good read for the basics. Some of the abilities have been nerf a tad such as weaken that only affects health now.
https://steemit.com/steemmonsters/@steemmonsters/steem-monsters-gameplay-mechanics-revealed
For understanding card levels if you choose to level things up this is the chart most use.
https ://cdn.discordapp.com/attachments/486206423815028747/502509194583212046/Card_Level_SM.png
Card Order
Many times card order is a big deal.
My biggest mistake when I first started was leveling up a bunch of melee attack cards. Unless they have sneak or the current conflict is melee mayhem (melee attack anywhere) they can only attack from the first slot.
Range cannot attack in the first slot.
Magic can attack in any slot.
So as you learn you have one tank up front, and your range in the back unless they are getting taken out by someone with sneak then you might want something with some hp in the last slot that can still attack from that position.
You get a free booster pack for doing the dailies. What splinter you need to get 10 wins on changes. While before you could not get a new daily until you finished the current one I’ve seen an option I’ve yet to test to maybe get a new quest.
Buying
If you are going spend to go beyond your own starting level and cards there are two methods. Buying off the market from other players or opening boosters. Before doing that I would make sure to use different splinters and make sure this is the game for you and you find 2 or 3 that you really enjoy. The game is expected to change to every match being random combat rules and what splinters are active. I’m not sure if they are going back track on that a bit or not. We won’t know till Season 3 is out and there no ETA at this time.
If you’re a budget player that does not like to take chances its best to just buy from other players. At this time you can not bulk buy off their site so your stuck with buying and paying for each card 1 at a time or finding a already level up card and buying that. Sometimes people charge a premium and other times you can find a level up card at a discount. Only way to really know is to look at the price for level 1’s and use the xp chart
To bulk buy many use third party sites such as https://peakmonsters.com/. I find the site a bit laggy perhaps things have changed since. You can see this is one of many sites people use by joining the official Steem Monster discord https://discord.gg/CAFJRjY and checking out the channel sites-related-to-sm. You can also get the official discord link from one of steemmonsters such as this one https://steemit.com/steemmonsters/@steemmonsters/steem-monsters-common-card-fantasy-story-contest-winners-the-elven-cutthroat.
Otherwise just enjoy the free packs you get from dailies and when season 3 starts as we get season rewards at the end.
The game does require a small amount of RC per match. If you happen to have any issues and are not posting/commenting often they sometimes are understanding and help out if you just mention RC issues in tech-support on discord.
There is also a channel in their discord to call in an upvote once every 48 hours on SM related content. Some use that as way to fund themselves little by little.
Some also like to enter contests to try and win some cards. Contestkings has quite an extensive list if you are into contests that do not require resteems, follows, or upvotes. https://steemit.com/contestkings/@contestkings/contest-kings-verified-20th-november-2018. That would take a lot of RC thought to enter 40-50 contest a week. Many of them are meme/gif contest and some even give other rewards like steem/sbi or other stuff.