I'm biased towards Python - and the following suggestions have nice UIs but they are web-based - so please forgive me in advance ;)
After years working in Siebel (UI dev tools, transparent database interface, etc) moved over to Linux dev and was stuck for a while - finally settled on Flask (http://flask.pocoo.org/) a Python micro-framework, which is light (i.e. not as incomprehensible as Django ;) but comes with a lot of functionality if you need it. Jump in. Here's a good guide that mixes in Bootstrap to make a very appealing UI - http://flaskbook.com/
Alternatively, go all ERP with lots of built in business functionality and nice UI features and try ERP Next (https://erpnext.com/) - which I'm looking at right now. It has some poor documentation, but the dev guide for the underlying framework (Frappe) is pretty clear (e.g. https://frappe.io/developers/g...) and looks less scary.