Stock Buy Sell Automation Tool

I am thinking to start building stock bot that will auto buy and sell stock when reach certain profit margin. I am not talking about F&O or intraday. I want to focus on delivery segment. For this i am looking for broker that has ZERO brokerage on delivery and also provide API access to automate tasks. Anyone know any platform or service that provide this type of tool? I want to develop bot for this task and thought some steps that need to be done. 1- find stocks from some trusted sources that will be feed into Bot and used to buy from them. 2- fix some budget and in that budget buy ony 2-3 stocks at a time. 3- Try to sell stock when it reach certain profit. 4- If stock goes lower then buy some more to average. 5- Do this steps multiple time a day. Idea is to generate consistant profit even if it is very low and do multiple buy/sell everyday. Any idea or feedback will be appreciated.