What's your recipe? Is it fairly cheap, I have 3 other pets to feed and I only get payed $80 a month (I'm only 14) so I'm already paying a pretty penny.
Sorry, I missed this question as I've only just worked out to turn on alerts for if people quote me!
I don't know how much my exact recipe will help you if you're not in the UK, with regards to different products, but I'll explain the justification underneath to help you to see what you have available that's similar.
So my mix currently, pulled off my spreadsheet is:
700g country value rabbit
100g science selective rabbit 4+
500g science selective chinchilla
100g burgess chinchilla
640g natures touch degu
200g tetra pond fishsticks
Resulting in food which is 15.36% protein, 3.42% fat, and 15.97% fibre. I also pay attention to CaP ratios, but it's not a precise figure as not every food discloses.
What I aim for is mostly fibre-based (rather than grain-based) rabbit food. The country value isn't great for rabbits, but it is heavily fortified and highly palatable, meaning the gerbils really like it so I can be sure they're getting some base level vitamins and minerals. The SS rabbit is be better nutritionally, but they hate it
Then the rest of the stuff is chinchilla food. Sometimes I vary this with degu food, but due to degu sugar intollerances (which gerbils don't have) it's usually a little bit more expensive than chin food, so I only vary that for enrichment reasons rather than nutrition. Here I use a mixture of pellet-based food and that with a lot of forage (nature's touch) to increase enrichment. Gerbils are theoretically fine with a museli based food, but the best high fibre/ low fat diets for other species are nugget-based and also people often heavily overfeed muselis due to misjudging how much food is needed.
And then the main protein source I use is pond fishsticks. Now, this is the least natural food for them in terms of protein source, however in the UK it is the only real high protein low fat option out there. Cat food is high in protein but the fat % is just over half the protein %, and dog food the fat % is usually just under half - even using a tiny bit of the most suitable in the mix ended up with inappropriate end analysis.
The above ingredients are medium to high quality so buying them all at once is expensive. BUT gerbils eat such a tiny amount each day in total that longterm it balances out as incredibly cheap to feed them. Do remember though that same as other animals, if you switch from museli-based to fibre-based you will have to feed them amount relatively volumetrically, because fibrey stuff just takes up more physical room, and is less nutrient dense.
So my gerbils get that mix about 5x a week. And then the other 2 days a week they get more natural forage-based things. So really nice hay or dried grass, dried 'bunny herbs' plants, safe bits of tree (which they actually eat rather than just chewing) with or without leaves depending on safety and time of year, and mealworms. Sometimes I get free samples of horse forage too, which I bung in here. These are the more enriching days as the above nugget-based mix although nutritionally great is a bit boring to be the sole endless diet as they are naturally foragers and scavengers.
However if you don't have a tank, I would prioritise finding one. I don't know what sites you have there, but here Gumtree and Preloved are the best places to get tanks. Ex-fish tanks are fine, and you don't need any of the extra gubbins, only the tank, meaning that if you have transport you can often pick them up cheaply e.g. my 4ft one was only £20 plus the £5 I paid my friend for driving me to get it (as I don't drive). But if you can't get a suitable sized tank at all, I would say that gerbils aren't the pet for you right now, as it is an absolutely essential thing for basic levels of care.