There are a huge variety of options to you depending on what systaem you use, and these options can range from next to free to multi thousand dollar. You’d be surprised the quality of sound you can get from next to free setups. Do you have a Mac? If so, Garageband has lots of surprisingly high quality software instruments that you can use to supplement instruments you don’t have, such as drums and bass. There’s also software such as EzDrummer. Audacity is EXTREMELY powerful for being free. As far as the playing aspect, pick a key and go for it! Start with rhythm parts and then construct a lead part over that. You can construct near infinite lead parts from one 3-or-4-chord rhythm track. Just have fun with it!