If you don't want to trough the hard grind of adding 400+ new items' data&images by yourself but you also don't want to apply a patch to your rom,here is a solution

What you need:
-HexManiacAdvance latest version
-The text file attached to the post

STEP 0
Open your Fire Red Rom in HMA

STEP 1-Recognizing the Limiters
There are a few limiters that HMA items' table doesn't account for,to solve this issue,paste the following data wherever in your rom:
STEP 2-Go to after the last item of the item table
If you haven't changed the items table of vanilla FR,your last item will be the "Sapphire",thus crtl+G,to open the Goto function,type "Sapphire",now select the next line of that

STEP 3-Insert the data
Paste the content of the "Items data only" txt file,HMA will take care of repointing the table and of adjusting its limiter

STEP 4-Insert the Images
Paste the content of the "Items images" txt file

STEP 5-Compatibility with the CFRU
Replace the following files with their respective files find in the attachments:
Include/constant/items
Include/constant/tmshms

STEP 6(OPTIONAL)-Compatibility with the DPE
The list of items in the DPE is a bit different from the one in the CFRU,no worries I provide a file for that as well,it's called "items DPE",
rename it "items" and put in your DPE/Include folder

What does it's not included in this resource?
-The items description are not included,you have to write them yourself(or copy them from Bulbapedia)HMA can help you with this as well
-The few items that weren't recently added in the CFRU(X Sp.Def,Rusted Shield,etc)
-All the new items are decapped,while the old ones still aren't,you'll have to decap them manually

If you are worried some data got overwritten don't be,HMA never does

I am currently very busy so I can't explain exactly how the 2 txt file works,I will edit this thread in a few weeks and add a tutorial that explains everything well

I hoped this helped

When i insert the image data appear multiple errors, i follow all steps

Hi,

yes expanding this tutorial in more detail would be really helpful, because I have some questions:

1. Where do I have to put the different columns of the .txt-files? Or can I just copy-paste the content over everything that comes after "Sapphire"? Because there are other items like TMs and Berries.
2. Where do I copy-paste the content of "Items images"? Directly after the content of Items Data Only?
3. Where do I put the Item Descriptions?
4. Do I have to recompile my ROM with CFRU?

Thanks :)