The attack route that gives you the most resources is usually the best one. However, consider the colors of the buildings you will find. For example, if you are trying to collect medals for a blue Hero upgrade, concentrate on the routes with the most blue buildings. Note that esources are produced over time, while Medals for upgrades are difficult to earn.
Defenses
Besides the defensive turrets that are used to protect your HQ, you can tap the HQ to request troops from your clan mates or to build/upgrade your mech. Defend all the routes to your base. Focusing only on the best route is not recommended. The more buildings you have on a route, the resources your enemy will capture if their attack succeeds. The type of building does not matter. Use all your buildings for defensive purposes. Position them in front of attackers to slow them down. Strive to increase your survival chance. This will also chip away at their heroes' health down and increase your chances of killing them. Do not place your defensive turrets outside of a path, such as dropping them between two lanes to have both of them covered. When a turret is outside a lane, enemy heroes will not bother to attack it. Position non-combat buildings first then set towers (Mortar, Minigun, etc.) afterwards. This forces attackers to get their health droped when dealing with buildings that are less important and allow you to hit them hard later. Doing this will also give your turrets a chance to provide supporting fire for other buildings. Each turret or mine that you tap will have a red area around them. This represents their area of effect. Position higher range weapons such as the Mortar near the end to allow them to provide the best defensive value. Mines are very useful, as they can decimate the health of the attacking heroes. Tap "Shuffle" on both routes until they are very close to each other. The closer your routes, the more defensive bonuses you can get from the same weapons on all routes. Position mines so that two of them can work in tandem. Also try to keep as turrets and weapons within the mine's area of effect.
Free bonuses
You will be given a free chest (a VIP Chest if you make at least a Gem purchase) every three hours and a Premium chest every 24 hours. These chests contain cards that can be used to upgrade your heroes. Certain islands feature daily cards if you attack and win (Daily Cards islands, Daily Color Cards island or Alcatraz).
Heroes
Some troop types are strong against a particular type while weak against another. Choose heroes that get some sort of bonus against the enemy you are facing. Start by launching an attack from the map. The ones in the campaign are free. After tapping an island, look at the colors of the weapons and buildings you will encounter. Use heroes that are strong against that type of enemy. You can also consider building a balanced team, with as many hero colors as possible.
Player vs. player
To unlock the PvP option, repair the PvP Carrier. Because this costs 20,000, you will have to upgrade your HQ to level three and your Gold Storage.
Upgrades
Constantly upgrade your base and have your workers doing something. Build and unlock everything possible and begin working on upgrades. Consider upgrading them all to the same level before progressing to a new level so that you have a balanced base. You can watch a video advertisement to eliminate ten minutes of waiting time. If there are less than five minutes remaining, you can rush production for free. Begin by upgrading your Storage building, then follow up with everything else. If you are short on money and you have free workers, raid until you have enough money to upgrade. You can also upgrade your heroes. Any of them can be upgraded if you have the cards. There is a possibility that more common heroes will be just as useful as rarer ones if they are of a high enough level. Consider upgrading as many heroes as possible at first. The cost to do so is very low for the first two levels. Decide which heros you like the most and focus on them. If you constantly get cards for a specific hero which you do not like, he or she might still get better than the ones you are using if they are at a higher level.
Various Tips
Don't forget to use your character's special skill like, for example, 10% chance to avoid taking damage. Keep in mind that they're all specific to their characters, so you need to learn them all.
Mines can take up to 30% of your health, so stay clear of them.
One interesting aspect in Raid HQ is the fact that you can actually attack your own base and see how well it will hold. To do this, simply go to the world map, and click on your headquarters.
While you can get a lot of gold by winning a number of battles, you can also do it peacefully, by exploring distant parts of your island.
Farming is somewhat disabled in this game as all the enemies become stronger after you defeat them. It's a great challenge, though, for leveling up.
What characters you'll bring to the raid depends mainly on the type of enemy you're fighting. You don't need to have all three colors in your team if two or one will do the job.
One of the first things you ought to upgrade is your gold storage. It can fill up quite quickly.
You can watch some ads to decrease the time it takes for your building to get made.
Attacking...