Try to get good coverage of road around the first few towers you have. It’s incredibly important to have high attacking uptime — but also to have a long road. This allows your single target towers to deal with the speedy bois early before the slower ones arrive.
Make sure that your AoE towers try to hit the initial spawn, if possible.
Dart Towers can be utilized so they fire several volleys if you position it so that enemies arrive on one side early, then another later.
You don’t have to place every tile you get. Sometimes it’s fine to just let it go, so that you don’t take up valuable space. This is especially seen with the gardens.
Another incredibly important factor is to manage your gold income. You get 1 gold per round by default. Every 10 gold you hold, you get 1 additional income up to 3 times (so a total of 4 gold per round). Ideally you stay floating above 30 gold, spending excess gold on going through tiles.
Towers cards aren’t entirely random. You will always get at least x tower cards over y cards. This means that cycling through the tiles is valuable to get more towers. Again, just leave the “useless” tiles.
Make sure you don’t just put slowing traps all willy-nilly. You want to slow enemies while they’re in range of your towers. Ideally a trap will affect 2 tiles but sometimes it just touching a single one is fine.
You want to save as much gold as possible to get to 30 gold as fast as possible. At than point, you get 4 gold each turn. That means you can cycle through (and place) three cards each turn, while keeping your gold at or above 30. This is probably the most important “secret” to winning — placing three tiles each turn makes it much easier.
Put cannon towers near the start of your road to quickly weed out the weak guys, and put arrow towers near the back to focus fire on the fast guys that break out of the pack. Arrow towers are inefficient near cannon towers, because arrow towers target the weakest unit — but then the bomb obliterates them, wasting their shot.
You can think of the roads as damage buffers for your towers. Try to circle the road back to reuse towers twice — without doing this, it’s nearly impossible to win. When you unlock area of effect towers like the ballista, you’ll want to create road mazes to maximize their use.