Hy i have a few questions, this is my first time a...

As a fairly new grower myself my opinions are not based on years of growing, but I do know that watts=weight in lighting. The higher the light wattage, the bigger your buds will get. I would suggest picking up some more lights even if small LED's and it will make a difference. For vegging I use a 30w LED light, but once they go into flower I use a 650w light. I tried it with smaller lights, and they will flower, but the buds will be much smaller. Soil can be garden dirt, but if you are growing indoors you will need to either get very good soil, or you will have to spend on nutrients. I wish you good luck and a bountiful harvest.

25w LED is really weak to grow cannabis. Will want low light requirement strains. You might be able to get a full cycle but your yeild will be very low. Few grams for 4-5 months work. Your light will work for seedlings and beginning veg. So do have a couple weeks to save before would have to add more light or move outdoor. As for soil. It's free. It's every where. Key to soil if not worried about creating live soil or PH levels. Is make sure has lots of air pockets. Air is more important than moisture retention with cannabis. 1/2 part gravel, 1/4 compost, 1/4 dirt.

Well you can for one plant sure just that 25 watt LED is going to be a bit weak. Light is their food so its would be best if you could along the way in flower add a bit. DOnt expect more than about 30 grams if you avoid other problems Can you get the plant into sun at least part of the day?

That likely won't be enough light long term, can you scrounge up some CFL bulbs or get them into sunlight if your looking to stay lowest possible cost? Otherwise keep the light close and try to give them quality water. Good luck!