Singapore is an ideal budget travel destination for first time international travel. If you could club it with Malaysia then it is a whole trip. Thailand is another budget spot, where you can cover Bangkok and Phuket based on number of travelling days. Indonesia is a lovely spot where you can cover Bali, Java, Sumatra at a nominal rate. Nepal and Bhutan are great places for first time international travel where you can cover paro, imphal and Kathmandu. My first international trip four years ago was to Singapore where we clubbed Malaysia and covered many places. Kindly check the COVID travel rules and restrictions before booking and travelling.
Kindly check the above Tripoto link for more details
South East Asian Countries offer a host of wonderful travel experiences in a budget, you may plan for Singapore with Malaysia or Vietnam or Bali or Indonesia or Thailand etc. (If looking for still cheaper options, then Nepal, Bhutan and Sri Lanka are the options).