To help people struggling to beat the AI or online opponents, here are some tips from Darwin Kastle:
The plan when playing Star Realms is to get your deck to do the most powerful things possible in the shortest amount of time possible. This usually means being able to play either as many expensive and powerful cards as possible in a turn, or to make use of as many powerful ally abilities as possible in a single turn, or preferably, both. To accomplish these things, you need both an overall plan based on the early game and a plan that evolves as the game goes longer. There are 6 main aspects to the game’s strategy.
Game phases – As you play the game it’s important to realize that the game has different phases as play progresses and to be aware of what phase you’re in. This is easiest in the digital game because of the ability to check the contents of both you and your opponent’s deck every turn. If you’re not doing this, you should be.

Bases – It’s important not to let your opponent’s bases stay in play and for them not to let yours stay in play. Keep an eye on whether they’ve been adding bases to their deck or not. If they do pick up some bases, you need to pick up answers for them like Battle Pod, Imperial Frigate, Patrol Mech, etc. If your deck is developing nicely you will be able to handle their bases with your own bases, ally abilities and big ships, but don’t rely on that if your deck doesn’t have those measures fully in place yet. Prioritize adding game breaking bases to your deck. These are bases that blow the game open if left in play, like Recycling Station, Junkyard, Central Office, Barter World, Port of Call, Machine Base, and Brain World. In the right deck, cards like the Hive, Blob World and Fleet HQ can also run away with the game if your opponent hasn’t loaded up on combat enough.

Ally Abilities – An ally ability being triggered basically makes a card twice as good. It’s like adding another good card to your hand. Triggering your ally abilities is one of the biggest forms of card advantage in Star Realms. The obvious way to make this happen frequently is to stick to only one or two factions when acquiring cards. The next best thing is to get rid of the unaligned cards from your deck with scrapping. There are other special cards that can also help you hook up your allies more frequently like Recycling Station, Stealth Needle and Mech World.

Scrapping – In the early game, the only reason not to take scrapping over anything is if it will make you the loser in a race for a gamebreaking card like Brain World, Command Ship, Central Office or Machine Base. I will take Recycling Station over anything that costs five or less. (including scrapping). If your opponent clearly has better scrapping than you, you generally need to go hyperaggressive in hopes that they won’t survive long enough to reap the benefits of their scrapping. If you have the scrapping advantage and they go hyperaggro, be sure to prioritize outposts and authority gain early.

Varying value – It’s important to realize how unstable card values are. Taking a Defense Center on turn one is a relatively weak play. In a late game where your opponent is bludgeoning you, there is nothing you’d rather have than a Defense Center. If I have four trade in the early game I will usually take a good two cost card and an Explorer over any three cost card. By the midgame when Explorers lose their value this completely changes.

Single card strategies– Some cards are so powerful that it’s worth building your entire game plan around them. The most obvious example is if there is generically and obnoxiously powerful card in the Trade Row in the early game, such as Brain World, Command Ship or Central Office. If you acquire one of these cards in the first 5 or 6 turns of the game you will usually win. So immediately start taking Space Stations, Freighters, Patrol Mechs, Rams, Blob Wheels and Trade Pods to ramp up to them before your opponent can get them. In addition, if you can get an early Blob World or the Hive it might be worth taking Blob cards over anything at that point to raise the power level of your new base to a game breaker. If you ever manage to get both Embassy Yachts, you should take bases over anything and prioritize scrapping to get those non bases out of your deck. This is a good idea if you get one Embassy Yacht, but it becomes a winning gambit if you have two.

Hopefully this helps you stay alive in the Star Realms!