As Rostock… above mentioned, be aware that TM pistols have plastic slides due to japanese firearm laws. They are great for actuall games.
But if you’re goin for realistic backyard plinking at short distances you’d be better of with a metal slide. Go for something cheap that appeals to you, like a WE or KJW. Or even a Vorsk. At 10ft it doesnt really matter.
As for lubricants just go with something Ptfe or lithium for metal on metal, silicone grease for plastic parts, dont overdo it. Have a read around, dont spray your entire gun with silicone oil.
As for bb weight, well for garden plinking it doesnt matter much, .25 will do more then fine unless your garden is huge.