As for me:
NinjaTrader - lot's of features and well developed ecosystem.
Tradematic Trader - simple and user-friendly, you can create strategies without programming in visual strategy builder. C# code editor is also available. Quite low price.
If you know how to deal with API, check alphavantage.co. It's a provider of free APIs for realtime and historical data on stocks, forex, and cryptocurrencies. They have limits on available data and number of requests. In free version: 5 API requests per minute; 500 API requests per day.