If you have 150,000 denarii, then you have way too much money. You have the means to expand and gain victory, but lack the focus and offensive impetus to do so. Your bloated treasury means most if not all your governors will have terrible traits of extravagance. The game greatly increases the chances for this happening first at 50K, and increases the chances again at 100K, and yet again at 150K. There is no need to hoard so much cash.

You need a cohesive plan to expand to victory. You have a powerful navy, so USE it! Systematically blockade your enemies and put together an amphibious assault force to surprise attack enemies with port cities. If your troops are inferior, then send out a couple generals and recruit mercs to fill the gaps. You have no excuse to be defensive when you have a huge treasury, and a big navy. Decide how you want to fill out the 50 provinces you need, and begin with that end in mind.

Since the Romans are strong now, if you fight them, you will need to adjust your tactics and force composition to make up for the general lack of mobility of Greek troops vs Romans. Invest in artillery, particularly onagers, missile units: slingers and archers, and heavy cavalry: sarmatian cavalry and mercenary war elephants, and skirmishers or missile cavalry. Combining your heavy infantry with skirmishers, missiles, and a few units of onagers using fire should devastate most serious opposition.

You must be relentless. Send in 2 armies at a time, with at least 3 total generals in the force. Use 1 army as your primary strike force, the other as a source for fresh units and to scout and protect your primary force from relieving armies. Keep shuttling in primo units with your navy. Your economy is more than sufficient to support the end game, so focus on military action.