ESPP is sort of a free money to you if the terms are good.
And a 10% discount is terrific. Usually there is a minimum holding period, though.
Continue taking that deal -- it's an excellent one! -- but just institute a program of automatic selling. For example, on May 8 of every year (pick a random date), sell the shares that are 3 years old or older. Use the sale proceeds to dollar cost average into your reasonably well diversified alternative investment(s). Loop, repeat. Something like that works well. (Or, if you want to get slightly fancier, sell the shares that are 3 years old or older every 6 months -- on May 8 and November 8 of every year, for example. If there's a fixed trading charge, don't get too silly. A couple times per year is enough.)
Beyond your ESPP, here's what I would do:
1. Top up your and your spouse's CPF Special Accounts and, if applicable, Medisave Accounts. Claim the tax reliefs. Do that every year until you're no longer able. You might also consider Ordinary Account to Special Account conversions, depending on your housing aspirations. Stick with traditional CPF, not today's CPF Investment Scheme. (In the future CPFIS might get better, and I might change my mind, but it's best avoided right now since the investment choices are terrible.)
2. Assuming you are not a U.S. person, Singapore dollar cost average into VWRD or IWDA, as you prefer. At low or medium monthly purchases, Standard Chartered probably offers the best trading deal. At medium to high monthly purchases, Interactive Brokers probably offers the best trading deal.
VWRD is a reasonably low cost, globally diversified stock index fund, domiciled in Ireland (for tax efficiency) and traded on the London Stock Exchange. IWDA is substantially the same except without emerging market stocks. Dollar cost averaging means you pick some sustainable figure -- say, S$1,000 (or whatever) -- and buy that amount every month, reliably, for decades hopefully. You don't even look at the price. Dollar cost averaging automatically results in buying more when the price is relatively low and less when the price is relatively high. As your earnings improve, and cash starts to accumulate, you can decide to boost your monthly purchase amount, but only if the higher figure is sustainable.
3. If you accumulate cash above your UOB One account's high interest limit, use Singapore Savings Bonds (SSBs) as a helpful, reasonably high yielding, safe parking place.
That's it, really. Pretty simple.
