Employer match, then debt above 10%, then the emergency fund, then an HSA, an IRA, the rest of your plan at work, and finally a taxable brokerage.
Room you have not used
Each account has a yearly allowance that does not roll over. This year it is $7,500 for an IRA and $24,500 for a plan at work, both higher from 50.
The order
1One-month bufferOne month of spending, in cash. It keeps an unexpected bill off a credit card, which is what ends most payoff plans.
2401(k) employer matchWhatever your employer adds to your plan at work when you contribute. It is the only return here that arrives the day you claim it.
3High-interest debtAnything above about 10%. No portfolio reliably earns what a balance at that rate costs you.
4Emergency fundThe rest of your emergency fund, three to twelve months of spending depending on what you would have to recover from.
5HSAOnly with a high-deductible health plan. Untaxed going in, growing, and coming out for medical costs, which no other account does.
6Roth IRA / IRAUp to $7,500 this year. Above the income cap it is a backdoor Roth rather than a direct contribution.
7Max 401(k)The rest of your plan at work, up to $24,500 this year across a 401(k), 403(b), 457 or TSP.
8Mega Backdoor RothAfter-tax contributions converted to Roth, if your plan allows both. Worth asking HR, because most plans do not.
9Taxable brokerageNo allowance and no rules, which is why it is last. Everything above it is finished first.