Typically when cheating in a Windows game (ex: CheatEngine), the way to go about it is to attach to the process with a debugger (or any other tool that can read memory from the process), look at an integer value on the UI and search for that value in the process memory. You'll find potentially thousands of memory locations due to the value probably not being very unique, and a lot of memory available. Then you perform an action in the game that you know can change that value, and search again. If the memory has not been re-allocated in the meantime you will likely narrow down the memory address for the variable you're interested in. That's usually fairly easy for integer values or strings. It's harder (and slower) for floating point values, or values that you aren't sure of their representation in memory. This also fails for Java and C# if they are using a relocating garbage collector (some mobile GC implementations disable relocation for performance, some keep it on to minimize fragmentation problems); it will depend on how the game was made.
Depending on how the game developers implement resource tiles, map tiles could be an array of tile data, an array of REFERENCES to tile data, or even just a slipshod list of game objects and components in Unity that has no simple and easy-to-manipulate representation in RAM. At this point it starts heavily depending on how the game is implemented; what language or engine they used, etc. If they used Unity, their code is in C# and you can probably decompile it from the Assembly-CSharp.dll inside the APK, unless they obfuscated it (in C#'s case that would mean renaming all classes and variables to meaningless things like "A" instead of "TileMap". If it's written in Java, it's about the same effort and results. If it's C++ or Unity with IL2CPP then you will have to learn how to be a professional assembly-level reverse engineer to get anything useful out of it. If you aren't already, we're talking about multiple years worth of effort trying to learn how to do it.
If you luck out and it's unobfuscated C# or Java, your best bet is to modify that code directly to do what you need. For Unity APKs which do not use IL2CPP, the .Net DLLs will be present and you should be able to edit them to a certain extent using dnSpy. Unity does make some tweaks to these DLLs itself in order for prefab->script references to find and instantiate the proper classes (and other things like that), so there's a risk that you can break the game completely if you attempt this; I've only modified XNA games for Windows this way, personally.
For Java, I only know of jdGUI for decompiling code; I haven't found anything like dnSpy for Java yet.
For native code (compiled from C++ or IL2CPP) you will need a professional grade disassembler/decompiler such as IDA Pro. IDA Pro has a free version of their disassembler that will work on the x86 binaries that should be present in Android APKs (Android native code should normally include both ARMv7 and x86 native code since some Androids use x86. Most use ARM, which I don't believe is freely available in IDA's free version. Their decompiler is not free and will likely be far outside of your budget. Remember that if you modify the x86 binary you will have to run the modified version on an x86 processor, which likely means using the emulator since the vast majority of Android devices use ARM.
After that you have to figure out how to reconstruct an APK from your modified files and install it on your device. If the game has any security measures which try to validate its signature, you will have to find and defeat those during the modification step. I haven't done this myself so I'm not sure of what you might encounter.
