LFM 2.5 1.2B instruct, it's good at instruction following as long as the instruction is short and simple.

Gemma 4 E2B is even better than LFM but I don't know if you can fit it in 3GB.

Qwen 3.5 0.8B and 2B are smart but very inconsistent for instruction following.

If you need absolutely tiny models, check Gemma 3 270m and FunctionGemma, LFM 2.5 230m and Granite 4.0 350m. However those are very stupid models and whether they are feasible for you will depend on your use case.