@blackout5328
Never sail with more loot than you are willing to lose, regardless of how good you will become at some point you will make a mistake and when solo a single mistake at the wrong time can simply mean you sink. Go and sell in between, don't be greedy.
Regardless of what you are doing every so often Halt! Seek high ground and look around. Being unprepared for your interactions with others is a guaranteed demise.
Park properly is one of the most important aspects of being solo. How to do this is fairly simple, when you arrive raise your sails this can be done to come to an halt. If you used your anchor no problem, raise the sails and then raise the anchor. Place your ship parallel to the island, which means facing to open water with the added benefit of able to harpoon items on shore. The primary thing is to face open waters! This allows you to board your ship, drop sails and be moving. Reposition the ship at larger islands to be near you at any point so you can get to it quickly when you spot sails heading in your direction and additionally consider visibility from open waters if you can minimize that it reduces your risks.
Learn the sailing mechanics. Like what is known as dummy sails, point the sails straight if you do not have full bellow on the sloop. Anchor turns, how to make tight turns between rock formations, breaking line of sight to then change direction and a whole bunch of planning a head. Going in a straight line against the wind is a great move to gain distance, but should never be your only objective. Additionally do learn the wind benefits and flaws of the other ships, there are beautiful pictures people have made explaining this or videos you can look up. If they are not sailing optionally use that to your advantage.
Learn to do drive by sells, this is the act of passing by outposts and even the reapers hide out in short proximity; jump off with a piece of loot while your ship sails on, rush to the merchant and sell, then rush back to your mermaid to adjust course. If you learn to do this in combination with the above you can sell anything you place value in once in chase.
Learn to use the environment around you to your advantage. Rock formations, islands and even land based cannons. One of the strongest weapons in your arsenal is to get on a land based cannon be it in a tower or just one on the bigger islands, smash them with a anchor ball or chain shots: immobilizing them, follow up with as many cannonballs you can, then shoot over and delay them as much as possible. Another one is using the fact that you are ahead of them, try boarding and anchoring or even better pick up a keg* in one of the barrel formations and blow them up. Keep in mind you don't need to sink your opponents, you just need to delay them, make them work for it and get enough of an advantage to reach the next outpost to sell. Eventually most pirates will give up or you won't have any treasure to steal.
*I personally never carry kegs when solo, but it is a double edge strong weapon. Judge for yourself if you are willing to take the risk.
Movement is your biggest friend when solo! Standing still is your worst enemy, stay active, become better at the voyages and be as efficient as you can be. The quicker you are the less risks you take. If you want to PvE, become good at it.
Priorities are to be made, your ships safety and the items on board are more important than any item you have on the island, any voyage you have. As in literally drop anything you are holding and sprint to your ship at the sign of danger, be ready to take off or fight! If an area is heavily trafficked maybe move to a different one, abandon the voyage and put down a new one. One of the most favorable areas to PvE is the Roar, it is more challenging with the environment yet has additional benefits as well. I have sunk so many crews even solo, because they are to greedy!
Manage your own risks, what is acceptable for you or me are very different. Emissary flags attract more attention, doing world events attract more attention and so on.
Think out of the box, sometimes the best option is to be creative. Hide your treasure on an island in a bush or cave, while you sail off with your ship as a distraction... fight, sink far away and return to pick it up. Use a rowboat with your loot when you break line of sight have your ship sail off in one direction while you row away in another. There are no guarantees these or any tactic will work, but they do at times.
Above all, remember that this is a game. You will lose, you will win... just try having fun regardless of the outcome. Try out new things, don't write yourself off to quickly or underestimate what you as a solid can do! If you have nothing to lose, just try and do something you might not otherwise... in the end experience is your only true growth's in the game.
While I have soloed pretty much everything in this game, I still advice people to also sometimes to get a crew. You can use the LFG, Discord, Open crews or even the forums to find crews to join. Not only does it make it easier, while learning getting tips or even just seeing others play and following their lead can help. I understand the attraction of playing solo, but it is and remain the most difficult thing to do... even a duo on a sloop will feel much easier.
Good luck and happy sailing.